墨鋒 › Free tools › Survey Sample Size Calculator
How many responses does your report’s survey need? Enter the confidence level, acceptable margin of error and population size to get the number straight away.
Formula: n₀ = Z²·p(1−p) ÷ e²; with a population size, the finite population correction n = n₀ ÷ (1 + (n₀−1)/N) is applied.
Try Inkacuity’sForms, fill in other people’s surveys to earn points and swap for your own survey to be filled in. No sign-up.
Go to the form swapThere is no single answer. For a very large population, 95% confidence and a ±5% margin need about 385 responses; for class reports teachers often accept 30 to 100. If your teacher or supervisor sets a requirement, follow it.
Leave it empty and it is treated as very large. Beyond a few tens of thousands the sample size barely changes.
At 50% the variance is highest and the sample size largest, which is the most conservative setting. Use 50% if you have no pilot data.
Online surveys often get 30% to 60%; swapping surveys with others or asking friends can reach 80% or more. Be conservative so you do not send out too few.
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