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Sample Size

This calculator can be used to determine the minimum number of people that need to be interviewed in order to obtain results that reflect the target population to an acceptable level of accuracy.

How To Interpret The Results

For example, suppose you wish to carry out a survey to determine the percentage of respondents who would be likely to take up a new product offering. The target population from which you can randomly select your sample is known as 1,000. You wish to test your results at the 95% confidence level and you are prepared to accept a margin of error of ±5%.

The number of people that need to be interviewed is 278.



Population Size

This is the number of people from which you can choose your random sample.

When you have a large population (e.g. 20,000+) the calculated sample size only changes marginally.


Confidence Level

The degree of confidence in whether or not the true figure for the population lies within the confidence interval for the survey.

For example, a 95% confidence level indicates there is a 1 in 20 (5%) chance that the true population result falls outside the confidence interval range.


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