21.7 Anxiety. A particular psychological test is used to measure anxiety. The average test score for all university students nationwide is 85 points. Suppose a random sample of university students is selected and a confidence interval based on their mean anxiety score is constructed. Which of the following statements about the confidence interval is true?
(a) The resulting confidence interval will contain 85.
(b) The 95% confidence interval for a sample of size 100 will generally have a smaller margin of error than the 95% confidence interval for a sample of size 50.
(c) For a sample of size 100, the 95% confidence interval will have a smaller margin of error than the 90% confidence interval.