STAT TEST 3

What is the mean of the t-distribution? A. 100 B. 10 C. 1 D. 0 E. Can't be determined without additional information.

0

Two samples, each with n = 9 scores, produce an independent samples t statistic of t(16) = 2.00, p <.05 with one-tail test. If the effect size is measured using r2 , what is the value of r2 ? A. 0.50 B. 0.25 C. 0.40 D. 0.20

0.20

In a repeated-measures study with a sample of n = 9 participants, the difference scores have a mean of MD = 4.90 and s2 = 36. What is the estimated standard error for the study? A. 1.0 B. 2.0 C. 3.0 D. 9.0 E. None of the above.

2.0

The following data were obtained from a repeated-measures study of memory performance before and after drinking 2 cups of coffee. What is the value of mean difference MD for these data? Participant Before After #1 10 15 #2 4 8 #3 7 5 #4 6 11 A. 3.0 (or -3.0) B. 3.5 (or -3.5) C. 4.0 (or -4.0)

3.0 (or -3.0)

Two samples, each with n = 5 scores, have a pooled variance, sp2 = 40. What is the estimated standard error, s(M1-M2) for the sample mean difference? A. 4 B. 8 C. 10 D. 20

4

The results of a hypothesis test with the t-test for a single sample are reported as follows: t(42) = 3.18, p < 05, 2-tailed test. Based on this report, how many individuals were in the sample? A. 42 B. 41 C. 40 D. None of the above

41

An independent-measures study uses two samples of n = 25 participants in each group to compare two treatment conditions. What is the df value for the t statistic for this study? A. 24 B. 25 C. 26 D. 50 E. 48

48

The t-test for independent sample can be used to examine ____________. A. The mean difference between two treatment conditions in an experiment (e.g. a difference in performance of experimental group and control group). B. The mean difference between two populations in quasi-experimental designs (e.g., mean difference in attitudes to abortion between residents of the southern vs. northern states). C. The mean difference in stress level at the beginning and the end of semester in a sample of undergraduate students. D. The t-test for independent sample can be used to examine ____________. E. All of the above.

A & B

Which of the following research situations illustrates the type I error in hypotheses testing? A. A researcher rejected a true null hypothesis. B. A researcher rejected a false null hypothesis.

A researcher rejected a true null hypothesis.

The estimated standard error, s(M1-M2) in the t-test for independent samples ________________. A. Is computed based on the variances of both samples B. Is computed based on the variance of a larger sample C. Is computed based on the variance of the smaller sample D. Is computed based on the population variances, σ2 B. Is computed based on the variance of a larger sample C. Is computed based on the variance of the smaller sample D. Is computed based on the population variances, σ2

A. Is computed based on the variances of both samples

Which of the following is the correct null hypothesis for an independent samples t-test (assume 2-tails test)? A. There is no difference between populations represented by two samples (i.e., μ1 - μ2 = 0 or μ1 = μ2). B. There is a difference between populations represented by two samples (i.e., μ1 - μ2 ≠ 0 or μ1 ≠ μ2). C. There is no difference between two samples (i.e., M1 - M2 = 0 or M1 = M2). D. There is a difference between wo samples (i.e., M1 - M2 ≠ 0 or M1 ≠ M2). E. None of the above.

A. There is no difference between populations represented by two samples (i.e., μ1 - μ2 = 0 or μ1 = μ2).

A researcher selects a sample from a population with the mean anxiety of µ = 60 and administers a therapy treatment to the individuals in the sample. Which of the following is the correct statement of the alternative hypothesis for a two-tailed t-test for a single sample?

A. µ ≠ 60 (there is a significant effect of the treatment)

What is indicated by a large variance for a sample of difference scores (i.e., a large variance of D scores)? A. An inconsistent treatment effect and a high likelihood of a significant difference. B. A consistent treatment effect and a low likelihood of a significant difference. C. An inconsistent treatment effect and a low likelihood of a significant difference. D. A consistent treatment effect and a high likelihood of a significant difference.

An inconsistent treatment effect and a low likelihood of a significant difference.

Which of the following statements is true about the relationship between the p level, the size of the critical region, and the risk of a Type I error? A. As the p level decreases (e.g., from .05 to .01), the size of the critical region increases, and the risk of a Type I error increases. B. As the p level decreases (e.g., from .05 to .01), the size of the critical region increases, and the risk of a Type I error decreases. C. As the alpha level decreases (e.g., from .05 to .01), the size of the critical region decreases, and the risk of a Type I error decreases. D. As the p level decreases (e.g., from .05 to .01), the size of the critical region decreases, and the risk of a Type I error increases.

As the alpha level decreases (e.g., from .05 to .01), the size of the critical region decreases, and the risk of a Type I error decreases.

For which of the following situations would a between-subjects research design be appropriate? A. Comparing patients' body temperature at the beginning and at the end of medical treatment B. Comparing self-esteem of students who participate in school athletics versus students who do not. C. Comparing mathematical skills of girls versus boys in elementary school age. D. All of the above E. B & C

B & C

If other factors are held constant, what is the effect of decreasing the variability of scores in a sample (i.e., decreasing a sample variance or standard deviation)? Hint: Look at the formulas for the estimated standard error and t-test for a single sample to figure out the answer. A. It will increase the estimated standard error and decrease the likelihood of rejecting H0. B. It will decrease the estimated standard error and increase the likelihood of rejecting H0. C. It will decrease the estimated standard error and decrease the likelihood of rejecting H0. D. It will increase the estimated standard error and increase the likelihood of rejecting H0.

B. It will decrease the estimated standard error and increase the likelihood of rejecting H0.

Which of the following is a fundamental difference between the t statistic and a z-score? A. The t statistic uses the sample mean in place of the population mean. B. The t statistic computes the standard error by dividing the standard deviation by n - 1 instead of dividing by n. C. The t statistic computes the standard error using a sample variability instead of the population variability. D. All of these are differences between t and z statistics.

C. The t statistic computes the standard error using a sample variability instead of the population variability.

A researcher obtains t = 2.01 for a repeated-measures study using a sample of n = 30 participants. Based on this t value, what is the correct decision for a two-tailed test? A. Fail to reject the null hypothesis with α = .05 but reject with α = .01. B. Reject the null hypothesis with α = .05 but fail to reject with α = .01. C. Reject the null hypothesis with either α = .05 or α = .01. D. Fail to reject the null hypothesis with either α = .05 or α = .01.

Fail to reject the null hypothesis with either α = .05 or α = .01.

Which of the following is an accurate definition of a Type II error? A. Failing to reject a false null hypothesis B. Failing to reject a true null hypothesis C. Rejecting a false null hypothesis. D. Rejecting a true null hypothesis

Failing to reject a false null hypothesis

Which of the following research situations would be most likely to use a within-subjects research design? A. Examining differences in reading comprehension among middle school children of two ethnic groups. B. Investigating the long-term effectiveness of a stop-smoking treatment by assessing participants'craving for cigarettes at the beginning and after 2 months of treatment. C. Examining academic performance of the Texas State University students by comparing their mean GPA to the national average GPA of undergraduate population in the U.S. D. All of the above.

Investigating the long-term effectiveness of a stop-smoking treatment by assessing participants'craving for cigarettes at the beginning and after 2 months of treatment.

When n is relatively small (less than 120), how does the shape of the t distribution compare to the normal distribution? A. It is almost perfectly normal. B. It is flatter and more spread out than the normal distribution. C. It is taller and narrower than the normal distribution. D. There is no consistent relationship between the t distribution and the normal distribution.

It is flatter and more spread out than the normal distribution.

If other factors are held constant, what is the effect of increasing the sample size? (Hint: Look at the formulas for the estimated standard error and t-test for a single sample to figure out the answer). A. It will decrease the estimated standard error and decrease the likelihood of rejecting H0. B. It will decrease the estimated standard error and increase the likelihood of rejecting H0. C. It will increase the estimated standard error and decrease the likelihood of rejecting H0. D. It will increase the estimated standard error and increase the likelihood of rejecting H0.

It will decrease the estimated standard error and increase the likelihood of rejecting H0.

In a repeated-measures experiment, each individual participates in one treatmentcondition and then moves on to a second treatment condition. One of the majorconcerns in this type of study is that participation in the first treatment mayinfluence the participant's score in the second treatment. How is this problem called? A. Individual differences problem. B. Homogeneity of variance problem. C. Order effect. D. Bi-treatment effect.

Order effect.

Two samples, each with n = 10, produced an independent sample t statistic of t = -2.97. Which of the following the correct decisions for a two-tailed test? A. Reject H0 with both, α= .05 and α= .01. B. Fail to reject H0 with both, α= .05 and α= .01. C. Fail to reject H0 with α= .05 but reject H0 with α= .01. D. Reject H0 with α= .05 but fail to reject with α= .01.

Reject H0 with both, α= .05 and α= .01.

An independent-measures research study examines gender differences in toddlers' verbal skills. The researchers tested verbal skills of nine 2-years old girls (i.e., n 1 = 9) and nine 2-years old boys (i.e., n 2 = 9). The data produced the t(16) = 2.38. Which of the following is the correct decision for a two-tailed hypothesis test with p <.05? A. Fail to reject the H0; there is a significant gender difference in toddlers' verbal skills. B. Reject the H0; there is a significant gender difference in toddlers' verbal skills. C. Fail to reject the H0; there is no significant gender difference in toddlers' verbal skills. D. Reject the H0; there is no significant gender difference in toddlers' verbal skills.

Reject the H0; there is a significant gender difference in toddlers' verbal skills.

A hypothesis test with a sample of n = 28 participants produces a t statistic of t = 2.81. Assuming a 2-tails test, what is the correct decision about the outcome of the test? A. The researcher can reject the null hypothesis with p < .05 but not with p < .01. B. The researcher can reject the null hypothesis with p < .01 but not with p < .05. C. The researcher can reject the null hypothesis with either p < .05 or p < .01. D. The researcher must fail to reject the null hypothesis with either p < .05 or p < .01. E. It is impossible to make the decision without more information.

The researcher can reject the null hypothesis with either p < .05 or p < .01.

A sample of n = 15 produces a single sample t statistic of t = - 2.22. If the researcher is using a two-tailed test for hypotheses testing, which of the following is the correct statistical decision? A. The researcher can reject the null hypothesis with α = .05 but not with α = .01. B. It is impossible to make a decision about H0 without more information. C. The researcher can reject the null hypothesis with either α = .05 or α = .01. D. The researcher must fail to reject the null hypothesis with either α = .05 or α = .01.

The researcher can reject the null hypothesis with α = .05 but not with α = .01.

Which of the following is the correct alternative hypothesis for an independent samples t-test (assume 2-tails test)? A. There is no difference between populations represented by two samples (i.e., μ1 - μ2 = 0 or μ1 = μ2). B. There is a difference between populations represented by two samples (i.e., μ1 - μ2 ≠ 0 or μ1 ≠ μ2). C. There is no difference between two samples (i.e., M1 - M2 = 0 or M1 = M2). D. here is a difference between wo samples (i.e., M1 - M2 ≠ 0 or M1 ≠ M2). E. None of the above.

There is a difference between populations represented by two samples (i.e., μ1 - μ2 ≠ 0 or μ1 ≠ μ2).

For which of the following situations would a repeated-measures design have themaximum advantage over an independent samples design? A. When many subjects are available and individual differences are large. B. When very few subjects are available and individual differences are large. C. When many subjects are available and individual differences are small. D. When very few subjects are available and individual differences are small.

When very few subjects are available and individual differences are large.

A sample of n = 25 is selected from the population with μ = 44, and a treatment is administered to the sample. After the treatment, the sample mean is M = 48 and the sample standard deviation, s = 12. Based on this information, what is the effect size evaluated by the estimated Cohen's d? A. d = 0.83 B. d = 0.75 C. d = 0.55 D. d = 0.33 E. None of the above.

d = 0.33

A researcher reports t(34) = 2.86, p <.05 2-tails test for a repeated-measures research study. How many participants are in the study? A. n = 17 B. n = 34 C. n = 33 D. n = 35 E. None of the above.

n = 35

A sample of n = 25 scores produces a t statistic of t = 3.00. Based on this information, what is the effect size evaluated by r2? A. r2 = 3/24 B. r2 = 3/25 C. r2 = 9/25 D. r2 = 9/33 E. None of the above.

r2 = 9/33

For a single sample t-test, what is the estimated standard error sM for a sample of n = 81 scores with SS = 72? A. sM = 3 B. sM = 6 C. sM = 8 D. sM = 9 E. None of the above.

sM = 8

What is the critical t value for a single sample t-test conducted on a sample of n =3 0 participants with p < .05, 1-tail test. IncorreA. t =2.787 IncorrectB. t = ±2.756 IncorrectC. t = ±2.462 CorrectD. t = ±2.797 IncorrectE. None of the above. A. t = 1.697 B. t = 1.699 C. t = 2.042 D. t = 2.045

t = 1.699

With α = .01, the two-tailed critical region for a single sample t test using a sample of n = 29 subjects would have boundaries of ______. A. t = ±2.787 B. t = ±2.756 C. t = ±2.763 D. t = ±2.462 E. None of the above.

t = ±2.763

Which of the following is the correct style of reporting the results of a hypothesis test with a t-test for a single sample and a measure of effect size using a t statistic, according to APA style? A. t(19) = 2.30, r2 = 0.42, p < .05 B. t(19) = 2.30, p < .05, r2 = 0.42, C. r2 = 0.42, t(19) = 2.30 , p < .05 D. t = 2.30, df = 19, p < .05, r2 = 0.42

t(19) = 2.30, p < .05, r2 = 0.42,

If a research report from an experiment investigating the effect of stress on memory states "t(30) = 2.01, p > .05, 2-tails test" then _______________. A. the researcher rejected H0 and found no significant effect of stress on memory. B. the researcher rejected H0 and found a significant effect of stress on memory. C. the researcher failed to reject H0 and found no significant effect of stress on memory. D. the researcher failed to reject H0 and found a significant effect of stress on memory.

the researcher failed to reject H0 and found no significant effect of stress on memory.

A researcher selects a sample from a population with the mean anxiety of µ = 60 and administers a therapy treatment to the individuals in the sample. Which of the following is the correct statement of the null hypothesis for a two-tailed t-test for a single sample? A. M = 60 (i.e., there is no significant effect of the treatment) B. µ = 60 (i.e., there is a significant effect of the treatment) C. µ = 60 (i.e., there is no significant effect of the treatment) D. M = 60 i.e., there is a significant effect of the treatment)

µ = 60 (i.e., there is no significant effect of the treatment)