Survey Sample Size
Estimate replies for a yes/no question at 50/50, from margin of error, 95% or 99% confidence, and an optional population.
Frequently asked questions
Why assume 50/50?
A yes/no split near half needs the most replies. If the true rate is more extreme, you need fewer.
What if I leave population blank?
The unlimited-population formula is used. A finite group slightly lowers the number.