How to Estimate Margin of Error

Surveys can give you valuable information about your customers, but this information is only valuable if it is accurate. Whenever you survey less than 100 percent of the population, you will have a margin of error. Knowing the margin of error will allow you to assess how accurate the information is, with a higher margin of error reflecting less accurate information. Calculate the margin of error using the percentage and number of respondents.

Instructions

1. Subtract the percentage of respondents from 1. For example, if the percentage of respondents was 80 percent you would subtract 0.8 from 1 to give you 0.2.

2. Multiply the result by the percentage of respondents. In this example, multiply 0.2 by 0.8 to give you 0.16.

3. Divide the result by the number of respondents. If there were 100 respondents in this example, you would divide 0.16 by 100 to get 0.0016.

4. Calculate the square root of the quotient. If the quotient is 0.0016, then the square root would be 0.04.

5. Multiply the product by 1.96. In this example, that would give you a margin of error of 0.0784 or 7.84 percent.

References

• "Survey Methodology"; Robert M. Groves; 2004