CHALLENGE ACTIVITY 7.2.1: Confidence intervals for population proportions Critical values for quick reference during this activity Confidence level Critical value 0.90 z* = 1.645 0.95 z* = 1.960 0.99 z* = 2.576 Jump to level 1 A poll reported 62% support for a statewide election with a margin of error of 1.3 percentage points. How many voters should be sampled for a 99%% confidence interval? Round up to the nearest whole number. Ex: 1234 + voters 3 Check Next