CHALLENGE ACTIVITY 7.2.1: Confidence intervals for population proportions. Critical values for quick reference during this activity. Confidence level | Critical value 0.90 2" = 1.645 0.95 2* = 1.960 0.99 2* = 2.576 377568 7850564.pap 7 Jump to level 1 1 A poll for a statewide election has a margin of error of 2.54 percentage points. How many voters should be sampled for a 99% confidence interval? Round up to the nearest whole number. Ex: 1234 0 voters