Selection bias occurs when multiple choice the population has been divided into strata portions of the population are excluded from the consideration for the sample cluster sampling is used instead of stratified random sampling those responding to a survey or poll differ systematically from the nonrespondents

The population has been divided into strata portions of the population are excluded from the sample.  

Explanation:

Sampling bias or coverage error is the term of sampling in social studies. Selection bias occurs when the researcher collects data from the population and that data has no meaning and value. This happened because the participants who are selected into the sampling are not selected fairly for both the groups. In the experimental group and control group, both the groups are representative of the sampling or general population. Theses groups represented each other as well. Both groups are equal. No one group represents higher than another group because it will make the findings distorted.

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