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 2* = 1.960 0.99 - 2.576 14214 2653566.qx3zay7 Jump to level 1 A poll reported 66% support for a statewide election with a margin of error of 2.42 percentage points. How many voters should be sampled for a 99% confidence interval? Round up to the nearest whole number. Ex: 1234 voters Check Next