A researcher wishes to estimate the proportion of adults who have high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.04 with 95% confidence if (a) she uses a previous estimate of 0.28? (b) she does not use any prior estimates? Click the icon to view the table of critical values. (a) n = (Round up to the nearest integer.) Table of critical values Level of Confidence, Area in Each Tail, Critical Value, ze (1 - a) -100% 90% 0.05 1645 95% 0.025 1.96 99% 0.005 2.575 - X