# Quiz 8: Confidence Intervals, Effect Size, and Statistical Power

Psychology

Q 1Q 1

Hypothesis testing tells:
A) what the size of an effect is.
B) which group differences are of practical importance.
C) whether two distributions overlap at all.
D) what results are significant, but no details regarding significant results.

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Multiple Choice

D

Q 2Q 2

Michelle is a cognitive psychologist studying reading times for stories that contain either consistent or inconsistent information.She runs 38 people through her study and concludes that reading times slow when coherence breaks occur in a story.Specifically, she concludes reading times slow by 6.9 milliseconds on average.Michelle's prediction is a(n):
A) interval estimate.
B) standard deviation.
C) point estimate.
D) sigma score.

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Multiple Choice

C

Q 3Q 3

Recent research published by Frumin and colleagues (2011) in the journal Science addresses whether females' tears have an effect on males.Imagine that exposure to tears lowered self-rated sexual arousal by 1.27 points, with a margin of error of 0.32 points.The point estimate is:
A) 1.27.
B) 1.27 +/- 0.32.
C) [0.95, 1.59].
D) 0.32.

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Multiple Choice

A

Q 4Q 4

A confidence interval is a(n) _____ that includes the population mean after repeatedly sampling.
A) point estimate
B) interval estimate
C) probability
D) hypothesis

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Multiple Choice

Q 5Q 5

Recent research published by Frumin and colleagues (2011) in the journal Science addresses whether females' tears have an effect on males.Imagine that exposure to tears lowered self-rated sexual arousal by 1.27 points, with a margin of error of 0.32 points.The point estimate is _____, while the interval estimate is _____.
A) 0.32; [0.95, 1.59]
B) 1.27; [0.95, 1.59]
C) 0.32; [-0.95, 1.59]
D) 1.27; [-0.95, 1.59]

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Multiple Choice

Q 6Q 6

Confidence in a point estimate _____, whereas confidence in an interval estimate _____.
A) is very high; is very low
B) is based on the alpha level used; is based on the margin of error calculated
C) cannot be articulated; is directly related to the size of the interval constructed
D) is very low; is very high

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Multiple Choice

Q 7Q 7

The range of raw scores contained in an 80 percent confidence interval will be _____ the range of raw scores contained in a 95 percent confidence interval.
A) larger than
B) smaller than
C) the same size as
D) smaller than or the same size as.

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Multiple Choice

Q 8Q 8

The sample mean is _____ the confidence interval.
A) at the beginning of
B) at the end of
C) in the center of
D) excluded from

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Multiple Choice

Q 9Q 9

It is known that the population mean for the verbal section of the SAT is 500 with a standard deviation of 100.In 2006, a sample of 400 students whose family income was between $70,000 and $80,000 had an average verbal SAT score of 511.The point estimate of the mean for this group is _____ and the 95 percent confidence interval for this group is _____.
A) 500; [501.2, 520.8]
B) 500; [490.2, 509.8]
C) 511; [501.2, 520.8]
D) 511; [490.2, 509.8]

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Multiple Choice

Q 10Q 10

Recent research published by Frumin and colleagues (2011) in the journal Science addresses whether females' tears have an effect on males.Imagine that exposure to tears lowered self-rated sexual arousal by 1.27 points, with a margin of error of 0.32 points.The interval estimate is:
A) 1.27.
B) +/- 0.32.
C) [0.95, 1.59].
D) 0.32.

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Multiple Choice

Q 11Q 11

What falls within the 95 percent confidence interval?
A) all the means we would expect to obtain 5 percent of the time when repeatedly sampling from a population
B) all the means we would expect to obtain 95 percent of the time when repeatedly sampling from a population
C) the true population mean
D) the null hypothesis population mean

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Multiple Choice

Q 12Q 12

What falls within a 90 percent confidence interval?
A) all the means we would expect to obtain 10 percent of the time when repeatedly sampling from a population
B) all the means we would expect to obtain 90 percent of the time when repeatedly sampling from a population
C) the true population mean
D) the null hypothesis population mean

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Multiple Choice

Q 13Q 13

When considering the results from an opinion poll, where several verbal expressions are rated for their level of annoyance, what is particularly useful about margins of error is that:
A) they tell us how accurate our data are.
B) they directly pinpoint a single value to estimate data.
C) the accuracy of the point estimate increases with the addition of the margin of error.
D) we can figure out more than one interval estimate for the same poll to see if they overlap.

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Multiple Choice

Q 14Q 14

According to a "how to stop bullying" website, 15 percent of students report experiencing bullying one to three times within the most recent month.Assume the standard deviation is 4.5 percent of students.Joseph collects data from 175 students at a medium-sized school in Iowa and finds that only 12 percent reported this rate of bullying.What is his 95 percent confidence interval?
A) [7.5, 16.5]
B) [11.33, 12.67]
C) [11.94, 12.06]
D) [14.53, 15.67]

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Multiple Choice

Q 15Q 15

If the sample mean is 56.2, with an upper limit to the confidence interval of 62.74, what is the lower limit?
A) 6.54
B) 49.66
C) 52.46
D) 56.20

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Multiple Choice

Q 16Q 16

Assume for a given study that the null hypothesis asserts the expected value of a phenomenon is 10.A research study results in a 95 percent confidence interval reported as [7.142, 9.865].What decision should be made based on this confidence interval?
A) Reject the null hypothesis.
B) Fail to reject the null hypothesis.
C) Retain the null hypothesis.
D) Perform a hypothesis test before making a decision.

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Multiple Choice

Q 17Q 17

Assume for a given study that the null hypothesis asserts the expected value of a phenomenon is 100.A research study results in a 95 percent confidence interval reported as [98.76, 105.24].What decision should be made based on this confidence interval?
A) Reject the null hypothesis.
B) Fail to reject the null hypothesis.
C) Retain the null hypothesis.
D) Perform a hypothesis test before making a decision.

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Multiple Choice

Q 18Q 18

The statement "The findings based on a sample of 1000 participants were statistically significant, providing evidence for the hypothesis" would be strengthened by:
A) using convenience sampling.
B) hypothesis testing.
C) measuring effect sizes.
D) sampling university students.

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Multiple Choice

Q 19Q 19

An article in the journal Applied Nutritional Investigation reported the results of a comparison between a low-calorie soy-protein diet and a low-calorie traditional-protein diet (Liao, 2007).Twelve obese participants were randomly assigned to each diet.At the end of the diet period, those on the soy diet lost an average of 2.3 percent of their body fat (SD = 0.55), while those on the traditional diet lost an average of 1.22 percent of their body fat (SD = 0.50).If the sample size of this study is increased, the value of the test statistic would _____ and the effect size would _____.
A) increase; remain the same
B) decrease; remain the same
C) decrease; increase
D) increase; decrease

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Multiple Choice

Q 20Q 20

As sample size increases, the:
A) population mean increases.
B) standard error increases.
C) size of the test statistic increases.
D) size of the test statistic decreases.

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Multiple Choice

Q 21Q 21

As sample size increases, the:
A) standard error decreases.
B) test statistic decreases.
C) standard error increases.
D) standard deviation increases.

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Multiple Choice

Q 22Q 22

As sample size increases, the test statistic increases because the:
A) difference between the means increases.
B) overlap between distributions increases.
C) distance between distributions decreases.
D) standard error decreases.

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Multiple Choice

Q 23Q 23

Increasing sample size:
A) decreases the likelihood that we will reject the null hypothesis.
B) increases the likelihood that we will reject the null hypothesis.
C) has no effect on the likelihood that we will reject the null hypothesis.
D) makes it more likely that we will make a Type II error.

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Multiple Choice

Q 24Q 24

It becomes progressively easier to declare statistical significance as the _____ increases.
A) standard error
B) value of the critical cutoff
C) sample size
D) number of items on the instrument

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Multiple Choice

Q 25Q 25

Effect size assesses the degree to which two:
A) populations overlap.
B) populations do not overlap.
C) samples overlap.
D) samples do not overlap.

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Multiple Choice

Q 26Q 26

Measures of effect size:
A) are unaffected by sample size.
B) increase as sample size increases.
C) decrease as the difference between population means increases.
D) do not rely on sample means.

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Multiple Choice

Q 27Q 27

Effect sizes are affected by _____ and _____.
A) large standard deviations; large standard errors
B) standard deviations; variability of population distributions
C) standard errors; variability of population distributions
D) mean differences; variability of population distributions

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Multiple Choice

Q 28Q 28

Why are effect sizes rather than test statistics used when comparing study results?
A) Effect sizes, unlike test statistics, are not affected by sample size and thus ensure a fair comparison.
B) It is easier to average effect size than it is to average test statistics.
C) Effect sizes are based on standard error, while test statistics are based on standard deviation.
D) Effect sizes, unlike test statistics, account for sample size, thus ensuring an accurate comparison.

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Multiple Choice

Q 29Q 29

The larger the effect size, the:
A) smaller is the test statistic.
B) smaller is the sample size.
C) more two distributions overlap.
D) less two distributions overlap.

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Multiple Choice

Q 30Q 30

Effect sizes rely on comparison of a distribution of _____ rather than on a distribution of _____ and are therefore unaffected by sample size.
A) means; scores
B) scores; means
C) errors; residuals
D) residuals; errors

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Multiple Choice

Q 31Q 31

Cohen's d is one measure of:
A) statistical significance.
B) effect size.
C) clinical significance.
D) sample characteristics.

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Multiple Choice

Q 32Q 32

Cohen's d is the:
A) method for calculating confidence intervals for the z test.
B) difference between the sample means divided by the standard error.
C) standardized difference between group means.
D) measure of statistical power.

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Multiple Choice

Q 33Q 33

Imagine that a study of memory and aging finds that younger participants correctly recall 55 percent of studied words, older participants correctly recall 42 percent of studied words, and the size of this effect is Cohen's d = 0.49.This effect size indicates that the memory performance of:
A) older participants is approximately half a standard deviation above that of younger participants.
B) older participants is approximately half a standard deviation below that of younger participants.
C) younger participants is approximately half a standard deviation below that of older participants.
D) younger participants is significantly lower than that of older participants.

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Multiple Choice

Q 34Q 34

Mehl (2007) published a study in the journal Science reporting the results of an extensive study of 396 men and women comparing the number of words uttered per day by each sex.He found that on average women uttered 16,215 words a day and men uttered 15,669 words a day.The effect size calculated on the basis of his findings is Cohen's d = 0.07.This effect size indicates that the:
A) number of words uttered by the men and women significantly differed from one another.
B) women uttered a significantly greater number of words in a day than did the men.
C) means of the men and women overlap by only 7 percent.
D) means of the men and women are not even one-tenth of 1 standard deviation apart.

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Multiple Choice

Q 35Q 35

To remove the adjustment for the influence of sample size, Cohen's d uses the _____ rather than the _____ as part of its formula.
A) standard error; standard deviation
B) standard deviation; standard error
C) raw scores; standard scores
D) variance; raw scores

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Multiple Choice

Q 36Q 36

The formula for Cohen's d substitutes the _____ symbol for the _____ symbol used in the denominator of the z statistic formula.
A)

_{M}; B) ; _{M}C) _{M}; D) ; _{M}Free

Multiple Choice

Q 37Q 37

According to Cohen's convention, a value of _____ is a small effect size.
A) 0.2
B) 0.5
C) 0.8
D) 340

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Multiple Choice

Q 38Q 38

According to Cohen's convention, a value of _____ is a large effect size.
A) 0.2
B) 0.5
C) 0.8
D) 340

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Multiple Choice

Q 39Q 39

According to Cohen's convention, a value of _____ is a medium effect size.
A) 0.2
B) 0.5
C) 0.8
D) 340

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Multiple Choice

Q 40Q 40

Mehl (2007) published a study in the journal Science reporting the results of an extensive study of 396 men and women comparing the number of words uttered per day by each sex.He found that on average women uttered 16,215 words a day and men uttered 15,669 words a day.The effect size calculated on the basis of his findings is Cohen's d = 0.07.According to Cohen's conventions for interpreting d, this effect is:
A) small.
B) medium.
C) large.
D) so small as to be considered virtually no effect.

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Multiple Choice

Q 41Q 41

When Cohen's d is large (based on Cohen's conventions), the amount of overlap between the two distributions being compared is _____ percent.
A) 75
B) 53
C) 15
D) 0

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Multiple Choice

Q 42Q 42

If an effect is significant but the effect size for the difference between the two means is small (according to Cohen's conventions), about how much overlap will there be between the two distributions?
A) 99 percent
B) 85 percent
C) 50 percent
D) 15 percent

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Multiple Choice

Q 43Q 43

Imagine that a study of memory and aging finds that younger participants correctly recall 55 percent of studied words, older participants correctly recall 42 percent of studied words, and the size of this effect is Cohen's d = 0.49.According to Cohen's conventions for interpreting d, this effect is:
A) small.
B) medium.
C) large.
D) so small as to be considered virtually no effect.

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Multiple Choice

Q 44Q 44

A high degree of overlap between two distributions of approximately 95 percent is likely to result in a(n) _____ effect size.
A) small
B) medium
C) large
D) unconventional

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Multiple Choice

Q 45Q 45

If an effect is significant but the effect size for the difference between the two means is medium (according to Cohen's conventions), about how much overlap will there be between the two distributions?
A) 99 percent
B) 85 percent
C) 67 percent
D) 53 percent

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Multiple Choice

Q 46Q 46

A degree of overlap between two distributions of approximately 50 percent is likely to result in a(n) _____ effect size.
A) small
B) medium
C) large
D) unconventional

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Multiple Choice

Q 47Q 47

An overlap between two distributions of approximately 99 percent is likely to result in a(n) _____ effect size.
A) small
B) medium
C) large
D) unconventional

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Multiple Choice

Q 48Q 48

An overlap between two distributions of approximately 39 percent is likely to result in a(n) _____ effect size.
A) small
B) medium
C) large
D) unconventional

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Multiple Choice

Q 49Q 49

An overlap between two distributions of approximately 55 percent is likely to result in a(n) _____ effect size.
A) small
B) medium
C) large
D) unconventional

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Multiple Choice

Q 50Q 50

One of the roles of the researcher performing a meta-analysis is to:
A) determine how many studies were never published and find those studies.
B) throw out statistical outliers from the analysis.
C) decide on the criteria for the inclusion of studies in the analysis.
D) convince the reader of the existence of the effect of interest.

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Multiple Choice

Q 51Q 51

Meta-analysis involves:
A) finding all studies published on a topic, contacting the authors of the studies to request their original data, and then analyzing all the obtained data in one large analysis of variance.
B) finding all studies published on a topic, calculating the effect size for each of those studies, and averaging the effect sizes together to find the average size of the effect across all studies.
C) averaging all the test statistics from every possible study on a given topic.
D) attempting to recreate the experimental conditions of every published study on a given topic.

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Multiple Choice

Q 52Q 52

If a researcher performs a meta-analysis and finds that the mean d = 0.45, and the 95 percent confidence interval around this mean is (0.34, 0.56), what can the researcher conclude?
A) All future studies of this effect will find effect sizes somewhere between 0.34 and 0.56.
B) Averaging across all of the literature, there really is no effect.
C) There is a medium effect, but it is unclear what the direction of the effect is.
D) Averaging across all of the literature, there is a medium effect, and this effect is statistically significant.

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Multiple Choice

Q 53Q 53

If a researcher performs a meta-analysis and finds that the mean d = 0.11, and that the 95 percent confidence interval around this mean is (-0.04, 0.26), what could the researcher conclude?
A) All future studies of this effect will find effect sizes somewhere between 0.34 and 0.56.
B) Averaging across all of the literature, there really is no effect.
C) There is a strong effect, but it is unclear what the direction of the effect is.
D) Averaging across all of the literature, there is a strong effect, and this effect is statistically significant.

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Multiple Choice

Q 54Q 54

Following a meta-analysis, the researcher might decide to perform a(n) _____ to determine the number of null results that would have to exist to overturn any statistically significant effect found in the meta-analysis.
A) power analysis
B) file drawer analysis
C) effect-size analysis
D) hypothesis test

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Multiple Choice

Q 55Q 55

The ability to reject the null hypothesis given that the null hypothesis is false is:
A) a Type II error.
B) statistical power.
C) a false alarm.
D) a Type I error.

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Multiple Choice

Q 56Q 56

Statistical power is a measure of the ability to reject the null hypothesis when:
A) it is true.
B) it is false.
C) there are no significant differences.
D) the sample size cannot be increased.

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Multiple Choice

Q 57Q 57

Statistical power is calculated as 0.93.This means that if the null hypothesis is _____, there is a _____ percent chance of rejecting the null hypothesis.
A) false; 93
B) false; 7
C) true; 93
D) true; 7

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Multiple Choice

Q 58Q 58

The statistical convention for the minimal acceptable power is:
A) 0.95.
B) 0.90.
C) 0.80.
D) 0.75.

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Multiple Choice

Q 59Q 59

The minimum acceptable level of estimated power for a study is:
A) 0.95.
B) 0.80.
C) 0.45.
D) 0.10.

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Multiple Choice

Q 60Q 60

If there is less than a(n) _____ percent chance of rejecting the null hypothesis when it is false, there is insufficient power.
A) 50
B) 60
C) 80
D) 90

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Multiple Choice

Q 61Q 61

Statistical power is:
A) the strength of the research study.
B) the ability to find important results.
C) a combination of the distance between group means and distribution variability.
D) the percent of the comparison distribution that falls beyond the critical cutoff.

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Multiple Choice

Q 62Q 62

Before conducting a power analysis, a researcher should know the desired:
A) alpha level.
B) gender distribution.
C) standard error.
D) variance.

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Multiple Choice

Q 63Q 63

Before hypothesis testing and at the beginning of a study, a researcher is advised to conduct _____ because it _____.
A) a power analysis; tells the researcher the number of participants needed for trustworthy results
B) an effect size estimate; tells the researcher the number of participants needed for trustworthy results
C) a statistical significance; determines how meaningful the study results will be
D) alpha testing; determines how meaningful the study results will be

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Multiple Choice

Q 64Q 64

The practical use of statistical power is that it informs researchers:
A) whether they will find significant results.
B) how many participants are needed to conduct a study with findings they can trust.
C) whether they will find important results.
D) what effect size they can expect to find in conducting their study.

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Multiple Choice

Q 65Q 65

Alpha refers to:
A) statistical power.
B) the probability of making a Type II error.
C) the probability of making a Type I error.
D) effect size.

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Multiple Choice

Q 66Q 66

When alpha increases, both _____ and _____ increase.
A) standard error; power
B) power; probability of a Type I error
C) power; probability of a Type II error
D) probability of a Type I error; probability of a Type II error

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Multiple Choice

Q 67Q 67

If the expected direction of an effect is correct, then using a one-tailed hypothesis test instead of a two-tailed hypothesis test:
A) increases power.
B) decreases power.
C) makes power 1.0.
D) makes power 0.

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Multiple Choice

Q 68Q 68

According to the textbook, a(n) _____ test has more statistical power; however, a(n) _____ is more conservative.
A) one-tailed; two-tailed
B) two-tailed; one-tailed
C) one-tailed; effect-size
D) effect-size; hypothesis

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Multiple Choice

Q 69Q 69

A researcher interested in the effects of humor on memory randomly assigns 16 participants to either the humor group or the no-humor group.The humor group reads humorous sentences and the no-humor group reads non-humorous sentences.On a later memory test, the researcher finds that in terms of the direction of the means, the humor group had better memory than the no-humor group, but this effect was not significant (p = 0.06).What should this researcher do?
A) She can attempt to increase her statistical power by using a two-tailed hypothesis test rather than a one-tailed hypothesis test.
B) She can abandon the study of humor on memory because given her results it is obvious that humor has no effect on memory.
C) Because the effect looks as though it is barely missing significance, she can just treat it as though the effect exists and communicate this exciting effect to her colleagues.
D) Because the effect looks as though it is barely missing significance and her sample size is fairly small, she can increase her sample size to increase her statistical power to detect the effect.

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Multiple Choice

Q 70Q 70

Which of the following does NOT increase statistical power?
A) increasing alpha
B) using a two-tailed hypothesis
C) increasing sample size
D) exaggerating differences between levels of the independent variable

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Multiple Choice

Q 71Q 71

Which of the following does NOT increase statistical power?
A) increasing alpha
B) using a one-tailed hypothesis
C) increasing sample size
D) reducing differences between levels of the independent variable

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Multiple Choice

Q 72Q 72

Which of the following does NOT increase statistical power?
A) increasing alpha
B) using a one-tailed hypothesis
C) decreasing sample size
D) exaggerating differences between levels of the independent variable

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Multiple Choice

Q 73Q 73

Which of the following does NOT increase statistical power?
A) decreasing alpha
B) using a one-tailed hypothesis
C) increasing sample size
D) exaggerating differences between levels of the independent variable

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Multiple Choice

Q 74Q 74

Increasing sample size does NOT:
A) increase statistical power.
B) decrease standard error.
C) increase the magnitude of the test statistic.
D) decrease statistical power.

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Multiple Choice

Q 75Q 75

If the mean difference between levels of the independent variable are exaggerated, statistical power:
A) increases.
B) decreases.
C) stays the same.
D) gets closer to 0.

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Multiple Choice

Q 76Q 76

A behavioral neuroscientist is testing the effects of adrenaline on memory using a group of 12 rats.The researcher is unsure about how much adrenaline might produce an effect on memory.One group of rats will be injected with placebo saline (0 micrograms of adrenaline).The other group will be injected with a dose of adrenaline.When deciding between a 2-microgram dose or an 8-microgram dose (both of which are safe), the researcher opts to use the 8-microgram dose.The researcher has:
A) made a Type II error.
B) exaggerated the difference between the levels of the independent variable, thereby increasing statistical power.
C) exaggerated the difference between the levels of the independent variable, thereby decreasing statistical power.
D) given the rats an overdose of adrenaline.

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Multiple Choice

Q 77Q 77

Using a one-tailed test allows us to increase statistical power over a two-tailed test because it:
A) divides the alpha into two tails but only focuses on one of those tails.
B) divides the alpha into two tails, which reduces the size of each.
C) puts the entire alpha into one tail, increasing the chances of rejecting the null hypothesis.
D) puts the entire alpha into one tail, decreasing the chances of rejecting the null hypothesis.

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Multiple Choice

Q 78Q 78

A statistically significant difference between two groups indicates that all or most participants in one group are different from all or most of the participants in the other group.

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True False

Q 79Q 79

An interval estimate is based on a sample statistic and provides a range of plausible values for the population parameter.

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True False

Q 80Q 80

A point estimate offers an advantage over an interval estimate because it estimates the population parameter using a range of values rather than a single number.

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True False

Q 81Q 81

An interval estimate offers an advantage over a point estimate because it estimates the population parameter using a range of values rather than a single number.

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True False

Q 82Q 82

An interval estimate is based on a population parameter and provides a range of plausible values for the sample statistic.

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True False

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True False

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True False

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True False

Q 86Q 86

Increasing the number of scores in a sample from 10 to 20 increases the width of a confidence interval to estimate the population mean.(Assume that all other factors are held constant.)

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True False

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True False

Q 88Q 88

Increasing the number of scores in a sample from 10 to 20 decreases the width of a confidence interval to estimate the population mean.(Assume that all other factors are held constant.)

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True False

Q 89Q 89

If the population mean falls within the 95 percent confidence interval, one should reject the null hypothesis.

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True False

Q 90Q 90

If the population mean falls within the 95 percent confidence interval, one should fail to reject the null hypothesis.

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True False

Q 91Q 91

If the population mean falls outside the 95 percent confidence interval, one should fail to reject the null hypothesis.

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True False

Q 92Q 92

If the population mean falls within the confidence interval, this means it is plausible that the sample comes from the null hypothesized population.

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True False

Q 93Q 93

If the population mean falls within the confidence interval, this means it is not plausible that the sample comes from the null hypothesized population.

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True False

Q 94Q 94

As sample size increases, the standard error decreases, resulting in a larger test statistic.

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True False

Q 95Q 95

Both effect size and the value of the test statistic are unaffected by changes in the sample size (holding other factors constant).

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True False

Q 96Q 96

As sample size increases, the standard error decreases, resulting in a smaller test statistic.

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True False

Q 97Q 97

If a real difference exists between a sample and the comparison distribution, that difference is necessarily important and meaningful.

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True False

Q 98Q 98

Effect size indicates the size of the difference between the sample and the null hypothesized value, unaffected by sample size.

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True False

Q 99Q 99

Effect size indicates the size of the difference between the population and the null hypothesized value.

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True False

Q 100Q 100

The amount of overlap between two distributions can be decreased if their means are closer together.

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True False

Q 101Q 101

The amount of overlap between two distributions can be decreased if their means are further apart.

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True False

Q 102Q 102

The amount of overlap between two distributions can be decreased if the amount of variation within each population is reduced.

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True False

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True False

Q 104Q 104

Cohen's d indicates the difference between two means in terms of variance, not standard error.

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True False

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True False

Q 106Q 106

Meta-analysis includes an assessment of null effects, often called a file drawer analysis.

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True False

Q 107Q 107

Statistical power is a measure of the ability to retain the null hypothesis when it is true.

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True False

Q 108Q 108

Statistical power is a measure of the ability to reject the null hypothesis when it is false.

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True False

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True False

Q 110Q 110

Statistical power calculations help researchers know how many participants are needed in their study.

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True False

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True False

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True False

Q 113Q 113

Increasing N to increase statistical power is considered a suspect practice by statisticians.

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True False

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True False

Q 115Q 115

A study reports finding a "significant" difference between group means.What can be concluded about this report?
A) The findings must be very important.
B) To fully assess the importance and impact of the results, we must also have information about the spread of the distributions.
C) There is no way to tell the practical importance of these results.
D) The difference between group means is so small that there is no effect when the findings are generalized to the overall population.

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Multiple Choice

Q 116Q 116

The _____ estimate acknowledges the amount of uncertainty in the _____ estimate by reporting the margin of error.
A) interval; standard error
B) point; interval
C) interval; point
D) point; standard error

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Multiple Choice

Q 117Q 117

The interval estimate for two values overlaps.What might this indicate?
A) Both points may actually have the same value in the general population, although one appears slightly higher, possibly due to uncertainty of the sample.
B) The range between the two points absolutely represents a genuine difference in the general population.
C) Both points must be equal if there is any overlap among their interval estimates because of error in estimating the population from a sample.
D) There is no way to tell if the difference between the two points is genuine.

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Multiple Choice

Q 118Q 118

According to the video game industry's statistics, the average gamer is 34 years old.Imagine the standard deviation for age is 7.5 years.Leroy collected data on video gaming among people with new tablets or iPads to see if the mean age of that group is older or younger.He finds an average age of 36.5 years based on a sample size of 54.His 95 percent confidence interval is:
A) [34.58, 38.42].
B) [36.23, 36.77].
C) [33.88, 38.12].
D) [34.5, 38.5].

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Multiple Choice

Q 119Q 119

In calculating confidence intervals in a z distribution, start by finding the z scores centered around the:
A) population mean.
B) sample mean.
C) standard error.
D) sum of squares.

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Multiple Choice

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Multiple Choice

Q 121Q 121

A small difference between means may not be statistically significant with a small sample, but it could reach statistical significance with a large sample because:
A) the overlap between distributions grows as sample size increases.
B) as N increases, the standard error gets smaller, reflecting less variability in sample means, which allows greater sensitivity to detect small but significant differences.
C) as N increases, distributions get more heterogeneous, allowing small differences to be detected.
D) the difference between means gets larger as sample size increases.

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Multiple Choice

Q 122Q 122

A researcher is comparing the normal curve for two studies using the standard deviation for individual scores.Study 1 depicts two samples with means close together, while the means in Study 2 are farther apart.Which has a bigger effect size?
A) Study 1 because there is more overlap between distributions
B) Study 1 because there is less overlap between distributions
C) Study 2 because there is more overlap between distributions
D) Study 2 because there is less overlap between distributions

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Multiple Choice

Q 123Q 123

In Cohen's d, the farther apart the means of two distributions, the _____ the effect size, assuming the standard deviation is held constant.
A) more variable
B) less variable
C) higher
D) lower

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Multiple Choice

Q 124Q 124

In Cohen's d, the closer together the means of two distributions, the _____ the effect size, assuming the standard deviation is held constant.
A) more variable
B) less variable
C) higher
D) lower

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Multiple Choice

Q 125Q 125

A Cohen's d of -0.49 is what type of effect size?
A) large
B) medium
C) small
D) Because it is less than zero there is no effect

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Multiple Choice

Q 126Q 126

A Cohen's d of -0.85 is what type of effect size?
A) large
B) medium
C) small
D) Because it is less than zero, there is no effect.

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Multiple Choice

Q 127Q 127

A Cohen's d of -0.19 is what type of effect size?
A) large
B) medium
C) small
D) Because it is less than zero, there is no effect

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Multiple Choice

Q 128Q 128

Which of these is NOT a benefit of performing a meta-analysis?
A) It adds statistical power by examining the results of several studies at once.
B) It increases the chances of misinterpreting data by analyzing half of the studies.
C) It reduces the risk of misinterpreting many findings within a broad literature.
D) It identifies what research questions are still left unanswered.

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Multiple Choice

Q 129Q 129

Ideally, a statistical power analysis should be conducted _____ the study.
A) during
B) before
C) after
D) throughout

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Multiple Choice

Q 130Q 130

Glen has limited funds left in his grant to pay participants to be in his experiment.He wants to know how many participants he needs to detect a difference between conditions.What statistical technique would help him estimate how many participants he needs?
A) Cohen's d
B) alpha cutoff levels
C) statistical power analysis
D) statistical significance

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Multiple Choice

Q 131Q 131

Statistical power can be enhanced by decreasing the standard deviation in the sample.This can be accomplished by all of these EXCEPT:
A) working with a biased sample.
B) using a more reliable measure.
C) sampling a more homogeneous group.
D) working with a narrower, less variable, distribution of scores.

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Multiple Choice

Q 132Q 132

In completing a questionnaire on various global economic issues, 31 percent of randomly selected respondents identified the issues as largely associated with the United States.If the margin of error was ±5.6 percent, what is the interval estimate for the United States?
A) 25.4 percent
B) 26.2-37.8 percent
C) 25.4-36.6 percent
D) 31-36.6 percent

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Multiple Choice

Q 133Q 133

If a researcher runs the same study 20 times, the researcher would expect to find a mean in (or at) the _____ 95 percent of the time, with a p value of 0.05.
A) outliers of the distribution
B) exact same point
C) point estimate
D) confidence interval

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Multiple Choice

Q 134Q 134

A 95 percent confidence interval of [153, 167] is calculated.What is the sample mean?
A) 14
B) 160
C) 167
D) 181

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Multiple Choice

Q 135Q 135

The critical cutoffs for a 95 percent confidence interval are -1.96 and 1.96.What are the cutoffs for a 90 percent confidence interval?
A) -1.65 and 1.65
B) -1.76 and 1.76
C) -1.96 and 1.96
D) -2.12 and 2.12

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Multiple Choice

Q 136Q 136

Sample size can affect whether statistically significant differences are found, but sometimes in extremely large samples differences are found that are significant but of no real value or interest.What standardized value helps measure the size of the difference in relation to the variability of the data rather than to that of sample size?
A) alpha level
B) confidence interval
C) effect size
D) interval estimate

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Multiple Choice

Q 137Q 137

When comparing the difference between means for two distributions, what happens to the effect size if the variability within each distribution becomes smaller?
A) There is no change in the effect size.
B) The effect size decreases.
C) The effect size increases.
D) It is not possible to find based the information provided.

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Multiple Choice

Q 138Q 138

As effect size increases, the overlap between distributions being compared:
A) increases.
B) decreases.
C) remains the same.
D) Overlap is not compared for distributions.

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Multiple Choice

Q 139Q 139

Cohen's d measures effect sizes in terms of:
A) standard deviation.
B) standard error.
C) sum of squared error.
D) sample size.

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Multiple Choice

Q 140Q 140

A Cohen's d value of 0.2 indicates how much overlap between distributions?
A) no overlap
B) 53 percent
C) 85 percent
D) a medium amount of overlap

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Multiple Choice

Q 141Q 141

A Cohen's d value of 0.5 indicates what effect size?
A) small
B) medium
C) large
D) no effect

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Multiple Choice

Q 142Q 142

As the overlap between distributions being compared decreases, the effect size:
A) increases.
B) decreases.
C) remains the same.
D) Overlap is not compared for distributions.

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Multiple Choice

Q 143Q 143

Published literature tends to include significant findings, where the data were sufficient to reject the null hypothesis.This can lead to an inflated estimate of effect size when computing a meta-analysis.Rosenthal suggested that researchers test the level of inflation of their effect size calculations by:
A) conducting additional research that would more clearly assess the relationship between variables.
B) pressuring scholarly journals to publish more null findings.
C) computing a file drawer analysis to see how many null findings would be needed to remove the statistical significance found.
D) including studies in their meta-analysis that have strong effects only.

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Multiple Choice

Q 144Q 144

Which of the following is NOT a way to resolve issues with the file drawer problem?
A) replicating a study
B) evaluating publication bias
C) conducting a file drawer analysis
D) eliminating unpublished studies from analysis

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Multiple Choice

Q 145Q 145

By increasing statistical power, the probability of making a _____ error is _____.
A) Type I; 0
B) Type II; decreased
C) Type I; decreased
D) Type II; 0

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Multiple Choice

Q 146Q 146

Power can be thought of as the percentage of the distribution of means, centered around the sample mean, that falls:
A) outside of the null hypothesized distribution.
B) below the mean of the null hypothesized distribution.
C) above two standard deviations from the sample mean.
D) within the critical cutoff regions, where the null hypothesis can be rejected.

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Multiple Choice

Q 147Q 147

A power analysis reveals that the study being run has low power.Which method is NOT an appropriate way to increase statistical power?
A) Increase the alpha.
B) Increase the variance of the distributions.
C) Increase the N.
D) Decrease the standard deviation.

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Multiple Choice