Margin of Error
Error bars for percentages made easy
Requires macOS 10.4+
Margin of Error produces confidence intervals for percentages. You supply the observed percentage, the sample size, and the confidence level, and Margin of Error will you give you the upper and lower confidence limit. Use this whenever you want to convey the uncertainty in any estimate of percentage.
Using Margin of Error
To generate error bars on your percentage, enter the percentage you measured on the first line. On the second line, enter the sample size, that is, the total number of items you observed to calculate the percentage. On the third line, enter the confidence level you'd like for your error bars. Click on calculate or press return and your confidence level is shown below. You can copy and paste this into another application like your mail program or a word processor.
Error bars have never been easier!