Question

A sample of 25 seniors from a large urban school district has a mean Verbal SAT score of 450. Assume we know that the standard deviation of the population of verbal SAT scores for seniors in the district is S=100. A 90% confidence interval for the mean score u for the population of seniors is used. Which of the following will produce a confidence interval with a smaller margin of error?

A. Using a confidence interval of 95%

B. Using a sample of 100

C. Using an upper critical value of 99%

D. Using a sample of 15 seniors

E. Using any sample size smaller than 25

Answer 1

The margin of error is dependent only on the sample size assuming that the samples are completely random. In order for the margin of error to be reduced, the sample size must be greater than the population size. Therefore, the answer is
B. Using a sample of 100