Asample 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