American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Selection bias in research is defined as what?

1. Systematic exclusion of participants

2. Refusal to respond by participants

3. A method of random assignment

4. Incorrect classification of data

The correct answer is: Systematic exclusion of participants

Selection bias in research occurs when there is a systematic difference between the participants included in a study and those who are not, which can lead to misinterpretation of the findings. The correct choice encompasses this concept because it highlights the systematic exclusion of certain populations or individuals from the study. This exclusion can result in a sample that is not representative of the broader population, potentially skewing results and conclusions drawn from the research. When participants are systematically excluded, the characteristics of the included population may differ in meaningful ways from those who were excluded—this could pertain to health status, socioeconomic factors, or other relevant attributes. As a result, any associations or effects observed may not be generalizable, thus compromising the internal and external validity of the research. The other choices do not accurately define selection bias. For example, refusal to respond pertains more to measurement or response bias rather than selection bias itself. Meanwhile, random assignment is a method used to create comparable groups in a study, which is an approach to minimize bias rather than an indication of bias. Incorrect classification of data deals with data handling issues rather than the selection process of study participants.