Exit poll and related survey methodology -- 2012 general election

Key facts and methodology details about voter surveys in the Nov. 6, 2012, general elections:

  Sampling error: All samples are approximations. A measure of the approximation is called the sampling error. Sampling error is affected by the design of the sample, the characteristic being measured and the number of people who have the characteristic. If a characteristic is found in roughly the same proportions in all precincts ("non-clustered") the sampling error will be lower. If the characteristic is concentrated in a few precincts the sampling error will be larger. Gender would be a good example of a characteristic with a lower sampling error. Characteristics for minority racial groups will have larger sampling errors.

The table below lists typical sampling errors for this exit poll for non-clustered characteristics at the 95 percent confidence interval. No more than one time in 20 should chance variations in the sample cause the results to vary by more than this amount for non-clustered characteristics. However, non-sampling factors such as question wording and order and voter non-response may increase total error.



Margin of sampling error



plus or minus 15 percentage points

101 - 200


plus or minus 10 percentage points

201 - 500


plus or minus 7 percentage points

501 - 950


plus or minus 5 percentage points

951 - 2350


plus or minus 4 percentage points

2351 - 5250


plus or minus 3 percentage points



plus or minus 2 percentage points