CHALLENGE ACTIVITY 5.8.1: 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 361666.1905872.qx3zqy7 Jump to level 1 1 A poll for a statewide election has a margin of error of 4.86 percentage points. 2 How many voters should be sampled for a 99% confidence interval? Round up 3 to the nearest whole number. Ex: 1234 $ voters