Psych Stats_Exam 2 Practice Problems - Answers

7. Even if a treatment has an effect, it is still possible to obtain a sample mean after the treatment that is very similar to the original population mean. Which outcome is likely if this happens?    a  reject H 0 and make a Type I error     b  correctly reject H 0     c   fail to reject H 0 and make a Type II error     d  correctly fail to reject H 0     8. One sample has a variance of s 2 = 12 and a second sample has a variance of s 2 = 8. Which of the following most accurately describes the pooled variance for the two samples?     a  closer to 8 than to 12     b  closer to 12 than to 8     c   somewhere between 8 and 12     d  around 16     9. A researcher is examining whether daily exercise influences mood. The researcher assigns n = 12 individuals to exercise for three months and finds an average mood score of M = 22 with SS = 182 after three months for individuals in this group . A second group of n = 7 individuals assigned to a control group for the three months has a mood score of M = 19 with SS = 90. Which of the following is most consistent with the results of conducting a two-tailed independent- measures t test with α = .05?     a   t = +2.12 and fail to reject the null hypothesis     b   t = +2.12 and reject the null hypothesis     c   t = +1.58 and fail to reject the null hypothesis     d   t = +1.58 and reject the null hypothesis     10. If a repeated-measures study shows a statistically significant difference between two treatments with α = 0.01, what can the researcher conclude about measures of effect size?     a  The value of Cohen’s d is large.     b  The value of Cohen’s d is small.     c  The value of both Cohen’s d and r 2 are large.     d   A statistically significant effect does not necessarily indicate that the effect size will be large.