# Whats the deal with the margin of error?

A survey’s “margin of sampling error” tells you how far off the mark you could be in your estimate due to the fact that you talked to a sample of the country’s population instead of calling every single person. This is the part of total survey error that is actually measurable, thanks to the laws of statistics. There are other forms of error whose effects can’t be measured as precisely. An example of how to interpret a given margin of error (MOE): Say a survey finds that 73 percent of the public back the invasion of Iraq, and the survey’s margin of sampling error is plus or minus 3 percentage points. This means that 95 times out of 100, you would get a number between 70 percent and 76 percent, with 73 percent the best current estimate. The size of the sample is the primary factor affecting the size of the MOE, though not the only factor. The chart below provides an average figure for various sample sizes (assuming, of course, that the sample has been selected at random.) Reading this,