Statistics
Sample Size Calculator Guide
Required sample size for surveys.
Determines estimate precision.
Formula
n=(Z²×p×(1-p))/E². 95%,±5%:n=385.
Factors
- Higher confidence=larger
- Smaller margin=larger
- p=50% gives maximum
Frequently Asked Questions
Sample size?
n=(Z²×p×(1-p))/E². 95%,±5%:385.
Why matter?
Too small=unreliable. Too large=wasted.
Margin of error?
±range. ±5%=within 5 points of estimate.