# Answers to Test Yourself

Below are answers to the chapter Test Yourself feature.

(1) d (2) b (3) c (4) d (5) c (6) a (7) b (8) b (9) The Cognition class, where you scored one standard deviation above the mean (z=1). In the Research Methods class, you scored less than one standard deviation above the mean (z=0.8). (10) z=1(11) A z-score is a number that compares the original score to the mean of the distribution. It allows for better comparisons of scores from two (or more) different scales.(12) a.) 5% b.) 98% c.) 79%   d.) 47% (13) 85 (14) 6.7 (15) d (16) c (17) b (18) a (19) e (20) a (21)  a (22) a (23) In hypothesis testing, we are relying on a probability—not a certainty—to make a decision. Therefore, errors are possible. (24) The alternative hypothesis is: Staying up all night decreased your final exam scores. The null hypothesis is: Staying up all night increased your final exam scores or made no difference. This is a one-tailed test. (25) We can reject the null hypothesis that staying up increases or has no effect on your final exam scores. A z-score of -1.79 shows a probability of 4% (0.037) in the tail of the distribution of sample means, which falls below our alpha level. The results suggest staying up all night decreased your final exam scores. (26) Correct decision (27) Increase the sample size. Enlarging the sample size could result in obtaining a significant difference between groups that is based on subject differences unrelated to the study.