Question

A researcher wants to examine if practicing yoga reduces stress. She selected a sample of n = 30 participants and assessed a stress level of each participant before and after taking a yoga class. The results of the study are tested with a repeated-measures t-test p <.05, 1-tail. What is the alternative hypothesis for this test?

• A. There is no significant change in stress level after taking yoga class.

• B. There is a significant significant change in stress level after taking yoga class.

• C. There is no significant reduction of stress level after taking yoga class.

• D. There is a significant reduction of stress level after taking yoga class.

42. A researcher computed a single sample t-test on a sample of n = 26 participants and obtained t = 2.42. If the researcher is using a two-tailed test, which of the following is the correct statistical decision?

• A. Reject the null hypothesis with either p < .05 or p < .01.

• B. Reject the null hypothesis with p < .05 but fail to reject with p < .01.

• C. Fail to reject the null hypothesis with either p < .05 or p < .01.

• D. Reject the null hypothesis with p < .01 but fail to reject with p < .05.

39. in general, if the estimated standard error increases and the other factors are unchanged, what will happen to the value of t-test? (Note: this question applies to all three t-tests)

• A. The computed t will decrease (i.e., it will move toward the center of the t- distribution).

• B. The computed t will increase (i.e., it will move farther toward the tail of the t- distribution).

• C. It will stay the same; the t statistic is not affected by the estimated standard error.

38. A report describing the results of a repeated-measures t-test states that “t(22) = 1.71, p > .05, 2-tails test.” Based on this statement, what was the research conclusion made by the authors of the report?

• A. Fail to reject the null hypothesis and conclude there was a significant effect of treatment

• B. Reject the null hypothesis and conclude there was a significant effect of treatment.

• C. Reject the null hypothesis and conclude there was no significant effect of treatment.

• D. Fail to reject the null hypothesis and conclude there was no significant effect of treatment.

Answer 1

1) Answer: D. There is a significant reduction of stress level after taking yoga class.

Explanation: It is one tailed t-test hence the alternative hypothesis is there is a significant reduction of stress level after taking yoga class.

42) Answer; D. Reject the null hypothesis with p < .01 but fail to reject with p < .05.

Explanation:

Degrees of freedom= n - 1= 26 - 1 =25

obtained t = 2.42

Critical t at 0.05 significance level and 25 df = 2.060

Critical t at 0.01 significance level and 25 df =2.787

The obtaine t value less than 2.060 but greater than 2.787. Hence Reject the null hypothesis with p < .01 but fail to reject with p < .05.

39) Answer: A. The computed t will decrease (i.e., it will move toward the center of the t- distribution).

Explanation: If the estimated standard error increases and the other factors are unchanged, then the computed t will decrease (i.e., it will move toward the center of the t- distribution).

38) Answer: D. Fail to reject the null hypothesis and conclude there was no significant effect of treatment.

Explanation:The p-value of t-test is greater than 0.05. Hence we fail to reject the null hypothesis and conclude there was no significant effect of treatment.