Standard error
Sampling and inference · Mathematics
Study notes
Q: A poll of 1600 voters finds 55% support. Find the standard error of the proportion. SE(p̂) = √(0.55×0.45/1600) = √(0.2475/1600) = √0.0001547 = 0.01244. About 1.24 percentage points - the estimate 55% ± 2.5% is the 95% interval!