We Want to Estimate with 99 Percent Confidence the Percentage

We want to estimate with 99 percent confidence the percentage of automobile purchasers who are under 30 years of age. A margin of error of 5 percentage points is desired. What sample size is needed? In an earlier sample, we found a 99 percent confidence interval of purchasers under 30 years of age to be [.18, .27] (use this figure for the sample proportion) .

A) 104
B) 664
C) 392
D) 463