Margin Of Error For Proportions Calculator

Margin of error (MOE) for proportions is a measure of the reliability of an estimate. It indicates the range within which the true population proportion is likely to fall. Understanding and calculating MOE is crucial for making informed decisions based on survey data.

1. Enter the proportion you want to test.
2. Enter the sample size (n).
3. Select the desired confidence level.
4. Click ‘Calculate’.

The formula for calculating MOE for proportions is:

MOE = Z * sqrt[(P * (1 - P)) / n]

Where:

• Z is the Z-score corresponding to the desired confidence level.
• P is the proportion.
• n is the sample size.

Z-scores for common confidence levels

Confidence Level	Z-score
90%	1.645
95%	1.960
99%	2.576

• Always use a confidence level appropriate for your decision-making needs.
• Consider the sample size when interpreting the MOE. A larger n reduces the MOE.
• Remember that MOE is a measure of precision, not accuracy.

What is a good margin of error?

A smaller MOE indicates a more precise estimate. A ‘good’ MOE depends on the context, but as a general rule, aim for a MOE of 5% or less.

For more information, see:

• U.S. Census Bureau
• OpenStax