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Confidence Interval Calculator for Proportions

This calculator is used to find the confidence interval (or accuracy) of a proportion given a survey´s sample size and results, for a chosen confidence level.

How To Interpret The Results

For example, suppose you carried out a survey with 200 respondents. If 45% of respondents answered the question of interest in a particular way and your desired confidence level was 95%, the corresponding confidence interval would be ± 6.9%. That is to say that you can be 95% certain that the true population proportion falls within the range of 38.1% to 51.9%.

Calculator

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Sample Size

The number of respondents who answered the question.

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Observed Proportion

The percentage of respondents who gave the response you are interested in.

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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.

Results

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