Prepared by Elisabeth Lindsay.
The margin of error is a statistical measurement referring to the predictable level of error in any sampling. Surveys, for example, are typically presented with a predictable and built-in margin of error, which indicates the results are true, give or take a certain number, based on variables in the sampling.
In general, the margin of error is a way of expressing a recognized lack of precision or lack of confidence in certain information. Although typically not expressed statistically, in genealogy, it is important to recognize the margin of error — the potential for error — in sources of information. Derivative sources, for example, may be expected to have a higher margin of error than original source documents, but this does not diminish their value. Any time information is relayed from one source to another, the margin of error is increased. The best way to compensate for the margin of error in any source is through verification; that is, verifying the information with an original source document — or the most reliable source available, and/or comparing it across multiple sources.