Challenge activities 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 Jump to level 1 V 1 V A poll for a statewide election has a margin of error of 2.52 percentage points. 2 How many voters should be sampled for a 95% confidence interval? Round up V 3 to the nearest whole number. Ex: 1234 voters 4 2 Check Next Feedback