Why 95% confidence limits? (created 2002-05-06)

Dear Professor Mean, I've been working with small data sets for some neuroimaging research that have 5 treatment and 5 control participants. It is not unusual to have such small samples in this kind of work. My 95% confidence interval (CI) included zero; yet, the 85% confidence interval did not include zero. I know that the 95% CI is the common one, but I also know that others are used, but I don't know when to use them. Therefore, I'd like to know why we use 95% confidence limits all the time. When it is appropriate to use other CIs and the logic behind making such decisions.

This webpage was originally published at the StATS website, which is currently unavailable. There is a dispute about the ownership of these pages, so I am only able to include a brief excerpt from this page.

This work is licensed under a Creative Commons Attribution 3.0 United States License. This page was written by Steve Simon and was last modified on 2010-04-01. Need more information? I have a page with general help resources. You can also browse for pages similar to this one at Category: Confidence intervals.