In all likelihood, you have used a Likert scale (or something you’ve called a Likert scale) in a survey before. It might surprise you to learn that Likert scales are a very specific format and what you have been calling Likert may not be. Not to worry — researchers that have been doing surveys for… Read More »
Sample Size – How Many Completed Surveys Do I Need?
We get this question all of the time, and the quick answer is: it depends. We can help you determine what this depends on based on your desired confidence level, margin of error and the total population size. Here, we explain these variables and offer up some recommendations for the number of people you should get completed surveys from; also called the sample size.
The confidence interval is the percentage of time that you want the true outcome to fall within the margin of error. The standard for most studies is 95%.
The margin of error, expressed as a +/- percent, gives a range for which actual results should fall within. The smaller the margin of error, the more confidence one should have that survey results are accurate for the total population. The standard for most studies is +/-5%.
Population size is the total number of people from whom you are sampling responses.
You can reference the included table to see the number of responses that are recommended based on the total population size of your target audience.
| Population Size | Recommended Sample Size |
|---|---|
| 10 | 10 |
| 100 | 80 |
| 200 | 132 |
| 300 | 169 |
| 400 | 197 |
| 500 | 218 |
| 600 | 235 |
| 700 | 249 |
| 800 | 260 |
| 900 | 270 |
| 1,000 | 278 |
| 2,000 | 323 |
| 3,000 | 341 |
| 4,000 | 351 |
| 5,000 | 357 |
| 10,000 | 370 |
| 20,000 | 377 |
| 100,000 | 383 |
| 100,000,000 | 384 |
About: The recommended sample size is based on a 95% confidence level and +/-5% margin of error
For example, you own an ice cream shop and you want to survey your customers. If you have 500 customers (population size) and you want a confidence level of 95% and a margin of error of +/-5%, for an accurate survey you would want to get 218 completed responses (sample size) from your ice cream shop customers.
Happy surveying!
Apr. 17 
Apr. 5