Deck 13: The Comparison of Two Conditions

Question 1

In a signal-to-noise ratio, the "noise" represents the

A) difference between the means of both groups.
B) variability in means between the groups.
C) variability in scores within the groups.
D) number of participants in both groups.

Answer 1

C

Question 2

Harry is using an independent t test to compare the means of two groups. There are ten participants in each group. How many degrees of freedom would be associated with this statistical test?

A) 8
B) 9
C) 18
D) 19

Answer 2

C

Question 3

Uriel wants to know if the men in his class spend more time watching sports on television than the women. Uriel asks 13 women in his class to keep track of the number of hours they spent watching sports on television during a seven-day period. He asks 12 men in his class to do the same. What would be the degrees of freedom associated with the t test in this situation?

A) 13
B) 23
C) 24
D) 25

Answer 3

B

Question 4

A waitress is interested in whether she receives larger tips in general from her male customers than her female customers. She records the gender of the customer who paid the bill and the amount of the tip over a two-day period. Statistically speaking, the "noise" in this research scenario would be

A) the difference between the average tip amounts received on the first and second days.
B) the fluctuation in tip amounts received from male customers during the two-day period.
C) the difference between the average tip amounts received from the male and female customers.
D) the fluctuation in tip amounts received from the male and female customers.

Question 5

Significance tests have two components. They are:

A) size of effect; independence
B) independence; dependence
C) size of effect; size of study
D) p value; test statistic

Question 6

The t distribution gradually approximates _______________ as the sample size increases.

A) the bifurcated distribution.
B) the standard normal distribution.
C) (243)
C) the chi-square distribution.
D) both a and

Question 7

In which of the following situations would one use an independent t test?

A) A professor wants to know if one of his two Introduction to Psychology classes scored significantly higher than the other class on the same exam.
B) A professor wants to know if there was a significant improvement in test scores from Exam 1 to Exam 2 for one of his Introduction to Psychology classes.
C) An educator wants to know if students spend more time talking on the phone than studying during a typical day.
D) A researcher wishes to learn whether the oldest child in a family does significantly better on standardized tests than the youngest child in the family.

Question 8

A professor wants to compare the test scores of his two psychology classes (Class A and Class B). Each class has 20 students. The professor calculates a t value of 2.3 and concludes that Class B has a mean test score that is significantly higher than Class A. What is the effect size associated with this statistical test?

A) .12
B) .24
C) .35
D) .48

Question 9

The t test is used to compare the means from how many groups?

A) 2
B) 3
C) 4
D) 5

Question 10

With 8 degrees of freedom, Linda finds that the probability associated with her obtained t value of 1.9 is p =.047 (one-tailed). What should Linda conclude?

A) The means from both groups are not significantly different from each other.
B) The means from both groups are significantly different from each other.
C) The difference between the means of both groups has practical significance.
D) She did not have enough participants in her study.

Question 11

One can optimize and strengthen the power of a t test in all of the following ways, EXCEPT

A) by using stronger treatments to drive the means of the two groups farther apart.
B) by decreasing the effect size of the study.
C) by decreasing the variability within groups.
D) by increasing the total size of the study.

Question 12

Brian wants to compare the test scores in one class to the test scores in another class. Which test of statistical significance should Brian use?

A) Pearson r
B) an independent t test
C) a correlated t test
D) a point-biserial correlation

Question 13

Which of the following statistical tests would one use to compare the means from two groups?

A) Pearson r
B) t test
C) chi-square
D) z score test

Question 14

When the results in one group are not influenced by the results in the other group, the samples are considered to be

A) random.
B) independent.
C) dependent.
D) separate.

Question 15

In a signal-to-noise ratio, the "signal" represents the

A) number of participants in both groups.
B) number of participants minus some value.
C) variability in scores within the groups.
D) difference between the means of both groups.

Question 16

A waitress is interested in whether she receives larger tips in general from her male customers than her female customers. She records the gender of the customer who paid the bill and the amount of the tip over a two-day period. Statistically speaking, the "signal" in this research scenario would be

A) the difference between the average tip amounts received on the first and second days.
B) the fluctuation in tip amounts received from male customers during the two-day period.
C) the difference between the average tip amounts received from the male and female customers.
D) the fluctuation in tip amounts received from the male and female customers.

Question 17

Which of the following measures represents the "noise" component in the t test?

A) the population variance
B) the population standard deviation
C) the unbiased estimator of the population variance
D) the unbiased estimator of the population standard deviation

Question 18

Which of the following conditions will result in larger t values?

A) smaller difference between means/smaller within group variance
B) smaller difference between means/larger within group variance
C) larger difference between means/larger within group variance
D) larger difference between means/smaller within group variance

Question 19

The p value associated with a statistical test indicates __________ while the associated effect size indicates __________.

A) practical importance; statistical significance
B) statistical significance; statistical importance
C) statistical significance; practical importance
D) practical importance; practical significance

Question 20

The effect size computed for the t test is equivalent to ____________.

A) the Pearson r
B) the phi coefficient
C) the Spearman rho
D) the point-biserial correlation

Question 21

Explain the conceptual relationship: Significance test = Size of effect × Size of study.

Question 22

What is the difference between independent and nonindependent samples? Which t test would one use under each circumstance?

Question 23

Paul wants to know if students in his class spend more time watching basketball or football on television. Paul has 13 women and 12 men record the numbers of hours they spent watching football and basketball during a seven-day period. What would be the df associated with the t test in this situation?

A) 13
B) 23
C) 24
D) 25

Question 24

What does the p value associated with an obtained t value indicate?

Question 25

In a test of the impact of delay on recall, a researcher has two groups study a list of words. For the immediate recall condition, the researcher has the subjects recall the words immediately after the study period has ended. For the delay recall condition, the researcher has the subjects recall the words three minutes after the study period has ended. The researcher found that there was not a significant difference in the number of words recalled between the two conditions. The researcher decides to conduct the study again, this time using fifteen minutes as the delay between studying and recalling the list. The researcher is trying to optimize t by

A) increasing the total size of the study.
B) using the dependent t test rather than independent t test.
C) decreasing the variability of response within groups.
D) driving the means further apart.

Question 26

William has 20 students take a test on two different occasions. What would be the df if he wanted to compare the mean scores from both occasions?

A) 39
B) 38
C) 19
D) 18

Question 27

Rather than personally reading the research instructions to each subject, an investigator has the subjects listen to a tape recording of the research instructions. In this case, the researcher is trying to optimize t by

A) driving the means further apart.
B) decreasing the variability of response within groups.
C) using a paired t test rather than an independent t test.
D) increasing the total size of the study.

Question 28

Why is it as important to calculate the effect size in addition to evaluating the statistical significance of an obtained t value?

Question 29

Ed wants to know if students did significantly better on a test the second time they took it. Which test of statistical significance should Ed use?

A) Cohen's d
B) Pearson r
C) an independent t test
D) a paired t test

Question 30

Describe the three ways that one can strengthen or maximize t.

Question 31

What is meant by a "signal-to-noise ratio"? Why does this characterize statistical significance testing using the t test?