A sample is self-selected when the inclusion or exclusion of sampling units is determined by whether the units themselves agree or decline to participate in the sample, either explicitly or implicitly.
How Does Self-Selection Enter into a Sampling Design?
There are three main routes through which self-selection enters into a sampling design. The first is nearly ubiquitous, and the latter two are more preventable.
When survey units are chosen by surveyors, but these units nonetheless elect not to participate (also called refusal-related nonresponse), self-selection occurs. Nonresponse can occur in probability or nonprobability sampling designs. If many such units elect not to participate, the representativeness of the resultant observed sample can be called into serious question as it may result in nonnegligible nonresponse bias. Self-selection can occur at the ...