18. With statistical power of 95%, the researcher knowsthat in general
(a) the chance that the alternative hypothesis is true is 95%
(b) the P-value for the study will be 5%
(c) the chance that the null hypothesis is false is 5%
(d) there is a 95% chance that H0 will be rejected if it is nottrue.

19. A z-score indicates how many standard deviations avalue is above or below the mean.
(a) True (b) False

Use for questions 20 - 22. The U.S. Fish and WildlifeService reported that the mean length of
six-year-old rainbow trout in the Arolik River in Alaska is441 millimeters with a standard deviation
of 81 millimeters. Assume these lengths are normallydistributed.
20. What is the probability the length of a six-year-oldrainbow trout is less than 400?
(a) 0.51 (b) 0.3050 (c) 0.6950 (d) -0.51

21. What is the probability the mean length of 30 six-year-oldrainbow trout is less than 400?
(a) 0.3050 (b) 0.9972 (c) 0.0028 (d) 0.6950

22. What is the length of a six-year-old rainbow troutthat is at the 80th percentile?
(a) 457.20 (b) 505.80 (c) 372.96 (d) 509.04

23. A psychologist is concerned about the health ofveterans returning from war. She examines 20 veterans
and assesses whether they show signs of post-traumatic stressdisorder. What is the sample of interest?
(a) All veterans returning from war. (b) The 20 veteransexamined.
(c) All psychologists. (d) Veterans with post-traumatic stressdisorder.

24. Is the underlined value a parameter or statistic? Ina recent poll, 57% of the respondents supported a
school bond issue.
(a) Statistic (b) Parameter

25. According to the Internal Revenue Service, theproportion of federal tax returns for which no tax was
paid was 32.6%. As part of a tax audit, tax officials draw a simplerandom sample of 120 tax returns.
What is the probability that the sample proportion of tax returnsfor which no tax was paid is greater
than 40%?
(a) 0.0418 (b) 0.0495 (c) 0.9505 (d) 0.9582