The differences between two nonequivalent groups become a confounding variable. This is called selection bias.
Selection bias is the bias that results from choosing people, groups, or data for study in a way that prevents adequate randomization, preventing the sample from being representative of the population being studied. The selection effect is another name for it.
Most frequently, when the term "selection bias" is used, it refers to the distortion of a statistical analysis brought on by the sampling procedure. Some of the study's conclusions can be incorrect if the selection bias is not taken into account.
Sampling bias is a type of systematic error that arises from a non-random selection of a population, resulting in a biased sample by making some members of the population less likely to be included than others.
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