43. When doing an independent samples t-test, when MUST you pool the variance?

a. When the sample size is less than 30

b. When the samples are of unequal sizes

c. When you are performing a one-tailed test

d. When you are using an alpha level less than .05

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

a. Examine the development of vocabulary as a group of children mature from age 2 to age 3

b. Examine the long-term effectiveness of a stop-smoking treatment by interviewing subjects 2 months and 6 months after the treatment ends

c. Compare the mathematics skills for 9th-grade boys versus 9th-grade girls

d. Compare the blood-pressure readings before medication and after medication for a group of patients with high blood pressure

45. When conducting an independent measures t-test:

a. the medians of the two populations are assumed to be equal

b. the null hypothesis is rejected if the calculated t-statistic you compute is more extreme than the critical-t

c. only the .01 significance level should be used to increase power

d. all of the above

46. Each of the following is part of conducting an independent measures t-test, EXCEPT

a. Difference scores are found for each subject

b. The population variances are estimated

c. The comparison is made against a t-distribution

d. The variance of the distribution of differences between means is computed

47. Which of the following describes the effect of increasing sample size?

a.Measures of effect size and the likelihood of rejecting the null hypothesis both increase.

b.Measure of effect size increase, but the likelihood of rejecting the null hypothesis decreases.

c.There is little or no effect on measures of effect size, but the likelihood of rejecting the null hypothesis increases.

d.There is little or no effect on measures of effect size, but the likelihood of rejecting the null hypothesis decreases.

48. The standard error of the difference for the independent measures t-test is an estimate of:

a. Centrality

b. Normality

c. Variability

d. None of the above

49. If other factors are held constant, increasing the level of confidence from 95% to 99% will cause the width of the confidence interval to:

a. Increase

b. Decrease

c. Not change

d. There is no consistent relation between interval width and level of confidence

50. An independent-measures research study uses two samples, each with n = 15 participants. If the data produce a t statistic of t = 2.760, which of the following is the correct decision for a two-tailed hypothesis test?

a.Reject the null hypothesis with = .05 but fail to reject with = .01

b.Reject the null hypothesis with either = .05 or = .01

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

d.Cannot answer without additional information

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

a.Increase the likelihood of rejecting H₀ and increase measures of effect size

b.Increase the likelihood of rejecting H₀ and decrease measures of effect size

c.Increase the likelihood of rejecting H₀ and have little or no effect on measures of effect size

d.Decrease the likelihood of rejecting H₀ and have little or no effect on measures of effect size