Stat 201 Exam 3 Fall 2010 -Version 3 Key

Stat 201 Exam 3 Fall 2010 Version 3 KEY Page 1 of 11 1. Suppose that, ten years ago, the proportion of Pittsburghers that were vegetarian was 19%. To test whether its any different today, suppose I select a random sample of Pittsburghers. Based on my study, I calculate a confidence interval to be: ( .13 , .29 ) [Assume the appropriate Central Limit Theorem conditions were satisfied.] (a) Report the value of my sample statistic (my point estimate of the overall proportion of vegetarians in Pittsburgh today). [3 pts] Remark: This is exactly like exercise 5a on the practice exam, and exactly like review exercise 2a on page 11 of lecture 26, and just like review exercise 1a on page 10 of lecture 26. .21 i.e., the center of the interv al. NOT .19 -- statistic, not parameter. (b) Report my margin of error. \ [2 pts] Remark: This is exactly like exercise 5b on the practice exam, and exactly like exercise (e) on page 5 of lecture 25, and exactly like review exercise 2b on page 11 of lecture 26. .08 i.e., half the length of the interval. (c) Were my results statistically significant ? (Choose the best