8. What are the two assumptions of the related-samples t-test? 9. Why don’t we h

Question

8. What are the two assumptions of the related-samples t-test?

9. Why don’t we have to worry about progressive error with an independent-measures research design?

10. To demonstrate the effects of losing one night’s sleep on performance of complex tasks, a sample of n=30 college students was given a problem solving task at noon one day and again at noon on the following day. The students were not permitted to sleep between the two tests. For each student, the difference between the first and second score was recorded. For this sample, the students averaged MD = 6.3 points better on the first test, with SS for the difference scores equal to 3480.

Do the data demonstrate a significant change in problem-solving ability?

Use a two-tailed test with = .01.

H0: _____________ H1: _____________ df = _________ Critical region (tcrit): _____________ s2 = _____________ s(MD) Decision (check one): ____ reject H0 = ________________ tobt = ________________ ____ fail to reject H0

Conclusion (check one): ____ Sleep deprivation did significantly affect performance ____ Sleep deprivation did not significantly affect performance

If appropriate, compute and evaluate Cohen’s d:

11. A researcher studies the effect of cognitive psychotherapy on positive self-regard. The number of positive statements made about oneself is recorded for each participant during the first meeting. After eight weekly therapy sessions, the measures are repeated for each person. For the following data, determine whether there is a significant treatment effect, using a two-tailed test with = .05.

Participate Before Treatment After Treatment

A 7 10

B 6 13

C 9 12

D 5 8

H0: _____________ H1: _____________ df = _________ Critical region (tcrit): _____________ MD = ____________ s2 = _____________

SS = __________________ s(MD) = ________________ tobt = ________________

Decision (check one) ____ reject H0 ____ fail to reject H0 ____

Conclusion (check one) Cognitive psychotherapy did significantly affect positive self-regard ____ Cognitive psychotherapy did not significantly affect positive self-regard

If appropriate, compute and evaluate Cohen’s d:

12. A researcher studies the effect of a drug on the number of nightmares occurring in veterans with post- traumatic stress disorder (PTSD). A sample of PTSD clients records each incident of a nightmare for one month before treatment. Participants are then given the medication for one month, and they continue to record each occurrence of a nightmare. For the following hypothetical data, determine whether the drug significantly reduces nightmares. Use a one-tailed test, with = .05.

Clients Before Treatment During Treatment

A 6 1

B 10 2

C 3 0

D 5 5

E 7 2

H0: _____________

H1: _____________ df = _________ Critical region (tcrit): _____________ MD = ____________ s2 = _____________

SS = __________________ s(MD) = ________________ tobt = ________________ ____

Decision (check one):reject H0 ____ fail to reject H0 ____

Conclusion (check one):Treatment does significantly reduce nightmares ____ Treatment does not significantly reduce nightmares

If appropriate, compute and evaluate Cohen’s d:

Explanation / Answer

8. The two assumptions are

i. There is natural pairing between the data points in the first set of data and the second set.

ii. The pairs came from a random sample and each pair is independent from the other pairs.

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