Question 1

If an experimenter conducts a t test for dependent means with 10 participants and the estimated population variance of difference scores is 20,the variance of the comparison distribution is
A)20 / 10 = 2.0
B)20 / 9 = 2.2
C)400 / 10 = 40.0
D)400 / 9 = 44.4

Accepted Answer

The variance of the comparison distribution is calculated by dividing the estimated population variance of difference scores by the number of participants.

Question 2

Your professor asks you to update a manuscript with the results of a t test for dependent means and provides you with the following information: there were 19 people in the study,the t score was 4.36,and the result was significant at the .01 level.The best way to present this information would be
A)t (19)= 4.36,p < .05
B)t (18)= 4.36,p < .01
C)t (4.36),p (.05)
D)t (4.36),p (.01)

Accepted Answer

The correct way to present the information is to state the degree of freedom as n-1, so the degree of freedom is 18 (19-1). The t statistic of 4.36 exceeds the critical value of 2.861 (at the .01 level with 18 degrees of freedom) and the p-value is less than .01, which indicates a statistically significant result. Therefore, the correct presentation would be t(18) = 4.36, p < .01.

Question 3

A medium effect size (d)for a t test for dependent means is
A).20
B).40
C).50
D).80

Accepted Answer

A medium effect size (d) for a t-test for dependent means is generally considered to be 0.50, according to Cohen's conventions.

Question 4

The t test for dependent means is LEAST robust when
A)the population is highly skewed.
B)the population is normal.
C)there are more than 30 participants.
D)the population variance is small.

Accepted Answer

The t-test for dependent means is least robust when the population from which the samples are drawn is highly skewed. This is because the t-test assumes that the differences between paired observations are normally distributed, and significant skewness in the population can violate this assumption, potentially leading to inaccurate results.

Question 5

If a t test for dependent means is reported in a research article as "t (16)= 2.67,p < .05," then
A)the result is not significant.
B)there were 16 participants.
C)the t score was 16.
D)the t score was 2.67.

Accepted Answer

The t score is explicitly stated as 2.67 in the report "t (16)= 2.67,p < .05," indicating the value of the t statistic calculated for the test.

Question 6

A counseling psychologist developing a technique to reduce procrastination has students time their procrastination for a week and uses this as a pretest measure of procrastination. Students then attend a workshop in which they are instructed to do a specific warm-up exercise for studying by focusing on a pleasant activity. Students again time their procrastination for a week, and the time from this second week is the posttest measure.
-If the psychologist wants to see if there is a change (increase or decrease)in procrastination by 10 of the students who attended his workshop using the .05 significance level,the cutoff t score(s)would be
A)-.62,0,+2.62
B)+2.262
C)-2.262,0
D)-2.262,+2.262

Accepted Answer

Since the psychologist wants to see if there is a change in procrastination, a paired samples t-test should be used. The null hypothesis would be that there is no difference in procrastination before and after the workshop (mu d = 0), while the alternative hypothesis would be that there is a change (mu d ≠ 0).

Since the sample size is less than 30 and the population variance is unknown, the t-distribution should be used. With a significance level of .05 and 10 degrees of freedom (n-1), the cutoff t-score(s) would be -2.262 and +2.262. Therefore, the best choice(s) is D -2.262 and +2.262.

Question 7

A counseling psychologist developing a technique to reduce procrastination has students time their procrastination for a week and uses this as a pretest measure of procrastination. Students then attend a workshop in which they are instructed to do a specific warm-up exercise for studying by focusing on a pleasant activity. Students again time their procrastination for a week, and the time from this second week is the posttest measure.
-If the psychologist wants to see if there is a change (increase or decrease)in procrastination by students who attended his workshop,the appropriate description of "Population 2" (the comparison population)would be people whose
A)posttest scores will be lower than their pretest scores.
B)difference scores will be 0 or greater than 0.
C)difference scores will be 0.
D)difference scores will be smaller than their pretest scores.

Accepted Answer

Population 2, the comparison population, represents the scenario where there is no change in procrastination, meaning the difference between posttest and pretest scores is zero.

Question 8

The most likely way for a t test to be presented in a research article for a study with 25 participants is
A)t (25)< significant
B)t (25)= 3.01,p < .05
C)t (24)= 2.94,p < .01
D)t (24)< significant

Accepted Answer

The items below (# 37 - 39)are based on the following table from a research article. 11ea7a42_741a_6bbf_81a2_51410eefa54b_TB2971_00

Question 9

Professor Q has designed a repeated measures experiment.Which information does he NOT need when looking up the power of his planned study in a power table?
A)whether a one- or two-tailed test will be computed
B)number of difference scores
C)estimated population variance of difference scores
D)effect size

Accepted Answer

The estimated population variance of difference scores is not needed when looking up the power in a power table, as power tables typically require information about the test type, sample size, and effect size.

Question 10

based on the following table from a research article.

-Which of the following differences were significant at the .05 level?
A)Dominance
B)Independence
C)Conformity and Nurturance
D)All of the above

Accepted Answer

The answer of based on the following table from a...

Question 11

based on the following table from a research article.

-Which of the following statements is most likely to be true based on the results presented?
A)The hypothesis testing procedure probably used one-tailed tests.
B)The various scales probably all had just about the same population variances.
C)The t scores are all larger than the raw difference scores.
D)The hypothesis testing procedure was probably a t test for dependent means.

Accepted Answer

The table shows two sets of data with means, standard deviations, and t scores. This is characteristic of a t test for dependent means, which is used when comparing two related sets of data. Therefore, choice D is most likely to be true. Choices A and B cannot be determined from the table. Choice C is not true as t scores are typically smaller than raw difference scores.

Question 12

Difference scores are computed for
A)a t test for a single sample.
B)a t test for dependent means.
C)a t test for independent means.
D)all t tests when the degrees of freedom are less than 10.

Accepted Answer

Difference scores refer to the paired scores in a t test for dependent means, which compares the means of two related groups. It is not used in a t test for a single sample or independent means. The size of the degrees of freedom does not affect the use of difference scores in t tests.

Question 13

"Student's" t test was invented by
A)Philip Guinness.
B)William Gosset.
C)Jacob Cohen.
D)Joan Guinness.

Accepted Answer

"Student's" t test was invented by William Gosset, who was a statistician working for the Guinness brewery in Dublin, Ireland in the early 20th century. He published under the pseudonym "Student" due to company policy prohibiting employees from publishing outside of the company.

Question 14

A counseling psychologist developing a technique to reduce procrastination has students time their procrastination for a week and uses this as a pretest measure of procrastination. Students then attend a workshop in which they are instructed to do a specific warm-up exercise for studying by focusing on a pleasant activity. Students again time their procrastination for a week, and the time from this second week is the posttest measure.
-If the psychologist finds that the sum of squared deviations from the mean of the difference scores of the sample is 135,the estimated population variance would be
A)135 / 10 = 13.5
B)135 / 9 = 15.0
C)10 / 135 = .074
D)9 / 135 = .067

Accepted Answer

The formula to estimate population variance from sum of squared deviations is:
Estimated population variance = sum of squared deviations / degrees of freedom
Here, the sample has 10 students (pretest and posttest) and we are finding the variance of difference scores between pretest and posttest, so the degrees of freedom is 9 (10-1). 
Therefore, estimated population variance = 135 / 9 = 15.0. 
Hence, the best choice is B.

Question 15

Studies using difference scores tend to have larger effect sizes than studies using other research designs because
A)of the long-standing procedural bias in psychology to set up studies involving dependent means in such a way as to artificially favor large effect sizes.
B)the standard deviation of difference scores is usually low.
C)participants provide their own baseline,which increases the variance.
D)studies with dependent means usually use a larger number of participants,so larger effect sizes are easily detected.

Accepted Answer

The standard deviation of difference scores is usually low, leading to larger effect sizes.

Question 16

based on the following table from a research article.

-Which of the following differences were NOT significant?
A)Dominance
B)Independence
C)Conformity and Nurturance
D)None of the above-all were significant

Accepted Answer

The answer of based on the following table from a...

Question 17

If a t test for dependent means is reported in a research article as "t (38)= 3.11,p < .01," then
A)the result is significant.
B)the result is not significant.
C)you can assume a one-tailed test was used.
D)there were 39 degrees of freedom.

Accepted Answer

The t-value of 3.11 indicates a significant difference between the means. The degrees of freedom are 38, which suggests that the sample size was 40 (since df = n1 + n2 - 2 in a dependent t-test). The p-value is reported as p < .01, which means that the probability of obtaining this result by chance is less than .01. It is not clear from the information provided whether a one-tailed or two-tailed test was used.

Question 18

Which of the following is an assumption for the t test for dependent means?
A)The population variance is known.
B)The population mean is greater than the sample mean.
C)The population follows a normal distribution.
D)The sample follows a normal distribution.

Accepted Answer

The assumption for the t test for dependent means is that the population follows a normal distribution. The other options are not relevant to this test.

Question 19

If 15 participants take a pretest and a posttest and have a mean difference score of 1.5,and if the standard deviation of the comparison distribution is 0.5,the t score is A)0.5 / 1.5 = 0.33 B)1.5 / 15 = 0.10 C)1.5 / 0.5 = 3 D)1.5 / 0.5² = 6

Accepted Answer

The t score is calculated by dividing the mean difference score by the standard deviation of the comparison distribution, which is 1.5 / 0.5 = 3.

Question 20

The comparison distribution in a t test for dependent means is a distribution of
A)means.
B)differences between means.
C)means of difference scores.
D)dependent means.

Accepted Answer

In a t test for dependent means, the comparison distribution is based on the means of the difference scores (i.e., the differences between paired measurements). Therefore, the correct answer is C.

Quiz 7: Introduction to T Tests: Single Sample and Dependent Means

If an experimenter conducts a t test for dependent means with 10 participants and the estimated population variance of difference scores is 20,the variance of the comparison distribution is

Your professor asks you to update a manuscript with the results of a t test for dependent means and provides you with the following information: there were 19 people in the study,the t score was 4.36,and the result was significant at the .01 level.The best way to present this information would be

A medium effect size (d) for a t test for dependent means is

The t test for dependent means is LEAST robust when

If a t test for dependent means is reported in a research article as "t (16) = 2.67,p < .05," then

The most likely way for a t test to be presented in a research article for a study with 25 participants is

Professor Q has designed a repeated measures experiment.Which information does he NOT need when looking up the power of his planned study in a power table?

based on the following table from a research article. -Which of the following differences were significant at the .05 level?

based on the following table from a research article. -Which of the following statements is most likely to be true based on the results presented?

Difference scores are computed for

"Student's" t test was invented by

Studies using difference scores tend to have larger effect sizes than studies using other research designs because

based on the following table from a research article. -Which of the following differences were NOT significant?

If a t test for dependent means is reported in a research article as "t (38) = 3.11,p < .01," then

Which of the following is an assumption for the t test for dependent means?

If 15 participants take a pretest and a posttest and have a mean difference score of 1.5,and if the standard deviation of the comparison distribution is 0.5,the t score is

The comparison distribution in a t test for dependent means is a distribution of