Question

Explain how randomized-controlled trials overcome selection bias.

Answer 1

Selection bias refers to bias introduced by the selection of people, groups or data for analysis in an approach that proper randomization is not achieved, hence ensuring that the sample received is not representative of the population intended to be analyzed. On other hand a randomized-controlled trials refers to a study or an experiment conducted in such an approach that several sources of bias as possible are removed from the process.

Selection bias is usually controlled by randomization. The main motive of randomized trials is thus to assure that each individual holds an equal probability to be assigned to one or the other treatment. It eliminates bias in treatment assignment thus overcomes selection bias. Randomization also permits to balance known and unknown confounders thus help to make control and treatment groups as balanced as possible.