Scores on a certain test are normally distributed and a researcher wishes to estimate the mean score achieved by all students on the test. He was told that he would need a sample size of 100 to assure a 95 percent confidence interval with width=4. What is the sample size required if he is interested in constructing a 90% confidence interval with width=4?
A) 80
B) 6241
C) 71
D) 142