A sampling method is called biased if it systematically favors some outcomes over others. Sampling bias is sometimes called ascertainment bias (especially in biological fields) or systematic bias. Bias can be intentional, but often it is not.

What is an example of a biased sampling method?

For example, a survey of high school students to measure teenage use of illegal drugs will be a biased sample because it does not include home-schooled students or dropouts. A sample is also biased if certain members are underrepresented or overrepresented relative to others in the population.

What makes the judgment sampling method biased?

Judgment sampling is prone to researcher bias.

Because each sample is based entirely on the judgment of the researcher, there is room for human error that results in researcher bias. Researcher bias, also known as experimenter bias, is when the people performing the research end up influencing the results of a study.