Margin of Error
Error bars for percentages
Free
Margin of Error produces confidence intervals for percentages. You supply the observed percentage, the sample size, and the confidence level, and Margin of Error gives you the upper and lower confidence limits on the percentage. 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.
Error bars have never been easier!
For more details, check out the support page for Margin of Error.