E 7.2: Confidence intervals for population proportions CHALLENGE ACTIVITY 7.2.1: Confidence intervals for population proportions Critical values for quick reference during this activity. Confidence level Critical value 0.90 1.645 0.95 z* = 1.960 0.99 z* = 2.576 Jump to level 1 A poll for a statewide election has a margin of error of 4.46 percentage points How many voters should be sampled for a 99% confidence interval? Round up to the nearest whole number. Ex: 1234 $ voters