Reference (95 % confidence, p = 50 %)
| Margin of error | Responses |
|---|---|
| ±10 % | 97 |
| ±5 % | 385 |
| ±3 % | 1,068 |
| ±1 % | 9,604 |
For small populations (for example 10,000 customers), enter the population size to apply the finite population correction — 385 becomes 370. Use 50 % as the expected proportion when unsure; it gives the largest, safest sample.
Frequently asked questions
Does a bigger population need a bigger sample?
Only slightly; above about 100,000 the required sample barely changes.
What is the margin of error?
How far the survey result may be from the true value, e.g. ±5 percentage points.
Does it account for low response rates?
No, invite more people so the number of completed responses reaches the target.