Psychology Statistics Final Practice Exam Part 3

On average, what value is expected for the t-statistic when the null hypothesis is true?

0

What is the average value expected for the independent-measures t statistic if the null hypothesis is true?

0

A repeated-measures study comparing two treatments with a sample of n = 4 participants produces a mean of M = 18 with SS = 24 for the scores in the first treatment, a mean of M = 14 with SS = 10 for the scores in the second treatment, and a mean of MD = 4 with SS = 12 for the differences scores. What is the estimated standard error for the sample mean difference?

1

A researcher report describing the results from a repeated-measures study states that the data show no significant difference between the two treatments, t(10) = 1.65, p > .05. Based on this report, how many individuals participated in the research study?

11

An independent-measures study has one sample with n = 6 and a second sample with n = 8 to compare two experimental treatments. What is the df value for the t statistic for this study?

12

The results of a hypothesis test are reported as follows: t(15) = 2.70, p < .05. Based on this report, how many individuals were in the sample?

16

An independent-measure study with n = 6 in each sample produces a sample mean difference of 4 points and a pooled variance of 12. What is the value for the t statistic?

2

A repeated-measures study comparing two treatments with n = 4 participants produces MD = 2 and SS = 75 for the difference scores. What is the estimated standard error for the sample mean difference?

2.5

An independent-measures research study n = 5 participants in each treatment produces sample variances of 8 and 10, and a 2-point difference between the two treatment means. Give this information, what is the value of Cohen's d?

2/3

A sample with a mean of M = 40 and a variance of s^2= 20 has an estimated standard error of 1 point. How many scores are in the sample?

20

Using an independent-measures t, the 90% confidence interval for the difference between two population means ranges from 19 to 23. Based on this confidence interval, how big is the difference between the two sample means?

21 points

One sample has n = 5 scores and the second has n = 10 scores. If the pooled variance for the two samples is 30, what is the value of the estimated standard error for the sample mean difference?

3

An independent-measures study produces sample means of M1 = 20 and M2 = 17, and a pooled variance of 9. For this study, what is Cohen's d?

3/3

For a repeated-measures study comparing two treatments conditions, a researcher obtains a sample of n = 9 difference with a mean of MD = 4 and a variance of s2 = 36. What is the value for the repeated-measures t statistic for these data?

4/2

Two samples, each with n = 9 scores, produce an independent-measures t statistic of t = 2.00. If the effect size is measured using r2, what is the value of r2?

4/20

A sample of difference scores has a mean of MD = 5 with a variance of s2 = 100. If effect size is measured using Cohen's d, what is the value of d?

5/10

The following data were obtained from a repeated-measures research study. What is the value of SS for the difference scores? 1st: 10, 4, 7, 6 2nd: 11, 6, 9, 5

6

If other factors are held constant, how does sample size influence the likelihood of rejecting the null hypothesis and measures of effect size such as r2 and Cohen's d?

A larger sample increases the likelihood but has little influence on measures of effect size

Which of the following research situations would be most likely to use an independent-measures design?

Compare the mathematics skills for 9th grade boys versus 9th grade girls

For which of the following situations would a repeated-measures research design be appropriate?

Comparing pain tolerance with and without acupuncture needles

A researcher report describing the results from a reported-measures t test states that "t(22) = 1.71, p > .05." From this report, what was the outcomes of the hypothesis test?

Fail to reject the null hypothesis with a sample of n = 23 participants

For an independent-measures t statistic, what is the effect of increasing the number of scores in the samples?

Increase the likelihood of rejecting Ho and have little or no effect on measures of effect size

Which combination of factors would definitely increase the width of a confidence interval?

Increase the sample mean and increase the size of the sample

Which of the following will not increase the width of a confidence interval?

Increase the sample mean from MD = 2 to MD = 4

How does sample variance influence the estimated standard error and measures of effect size such as r2 and Cohen's d?

Larger variance increases the standard error but decreases measures of effect size

What value is estimated with a confidence interval using the repeated-measures t statistic?

The mean for a population of difference scores

Which of the following is a fundamental difference between the t statistic and a z-score?

The t statistic uses the sample mean in place of the population mean

What value is estimated with a confidence interval using the t statistic?

The value for an unknown population mean

With a = .05 and df = 8, the critical values for a two-tailed t test are t = ±2.306. Assuming all other factors are held constant, if the df value were increased to df = 20, what would happen to the critical values for t?

They would decrease (move closer to zero)

A researcher reports an independent-measures t statistic with df = 30. If the two samples are the same size (n1 = n2), then how many individuals are in each sample?

n = 16

A researcher conducts a hypothesis test using a sample from an unknown population. If the t statistic has df = 30, how many individuals were in the sample?

n = 31

A sample of n = 16 scores produces a t statistic of t = 2.00. Based on this information, what is the effect size evaluated by r2?

r2 = 4/19

A sample of n = 16 scores has a mean of M = 65 and an estimated standard error of 2 points. What is the sample variance?

s^2 = 64

The results of an independent-measures research study are reported as "t(22) = 2.12, p < .05, two tails. For this study, what t values formed the boundaries for the critical region?

±2.074