What is Selection Bias?
Selection bias is a type of bias that occurs when a sample of individuals is selected for a study in such a way that it is not representative of the population being studied This can lead to inaccurate results and conclusions being drawn from the data collected. Selection bias can take many forms, such as convenience sampling, non-random sampling, and biased selection of control groups. The most common type of selection bias is self-selection, which occurs when participants in a study select themselves for inclusion in the research.
Selection bias can lead to many different types of errors in research. It can lead to sampling bias, in which the results from a study may not be representative of the population under study. It can also lead to response bias, in which participants may not answer survey questions accurately or honestly. Selection bias can also lead to confounding, in which variables not taken into consideration can heavily influence the results of a study. Therefore, researchers must be careful to avoid selection bias in order to ensure reliable and accurate results.
Five Examples of Selection Bias
1. Non-Random sampling: Non-random sampling occurs when a sample is selected in a way that does not accurately reflect the population being studied. For example, a researcher may choose to sample only students at a certain university or participants from a certain age group.
2. Convenience sampling: Convenience sampling happens when a sample is taken from the most convenient population available. An example of this would be a researcher who chooses to survey only those who visit a certain website or shop at a certain store.
3. Lead time bias: Lead time bias happens when a study does not take into account the time it takes for participants to be included in the sample group. This can lead to inaccuracies in the results of the study.
4. Volunteer bias: Volunteer bias occurs when participants who are more motivated or interested in the study are more likely to volunteer, skewing the sample group.
5. Selection bias in surveys: Selection bias can occur in surveys if questions are not worded correctly or if certain population groups are not included in the survey. This can lead to inaccurate results.