A Sociologist Develops a Test to Measure Attitudes About Public

Multiple Choice

A sociologist develops a test to measure attitudes about public transportation.She wishes to compute a 90% confidence interval for the mean score on this test.It is believed that the standard deviation for these test scores will be 21.How many people should be given the test in order to achieve a margin of error of 10?

A) 11
B) 14
C) 12
D) 15
E) 13