Measuring Sub-Group Preferences
Sub-Groups: Size Matters
Soccer Moms, NASCAR Dads, Evangelical Christians, the Internet Married – we know that political strategists like to group voters into categories in order to target their candidate’s message. But election polls are limited in uncovering the vote intention or opinions of these microgroups because of their small size.
Journalists need to take into account that when subgroup results are reported, the sampling error margin for those figures is larger than the sampling error for results based on the sample as a whole. (see graph on this page) Journalists should identify the number of respondents in the subgroup, even for larger groups such as Democrats or men or Hispanics or senior citizens.
The following table shows the number of respondents in various subgroups from a statewide poll of a battleground state in the Midwest.
Sample sizes below 100 will have a large margin of sampling error – plus or minus 10 percentage points for a sample size of 100 and increasing as the sample size declines. Journalists should avoid reporting on groups this small unless there is a compelling reason to do so, and the only after consulting with an independent polling expert.
This information was developed by AAPOR as part of a comprehensive online journalism polling course created in partnership with NewsU, a project of the Poynter Institute and funded by the Knight Foundation. The course launched September 2007.
Download PDF Version