Question

If a researcher samples only a group of willing students versus a random group of students, would this cause a problem in evaluating the efficacy of his program? Why?

Answer 1

Yes, this would cause a lot of bias in evaluating the efficacy of his program because of following reasons:-

i) Only willing students may not form a unbiased opinion of the class because it would create a voluntery bias as only interested students would represent the whole class.

ii) it might happen that only a group of talented students willingly opt in then the researcher might be under the impression that the program was a real success but this might not be the case.

iii) Depending on the quality and number of willing students the conclusion might change, creating further problems and not having a unbiased opinion.

iv) Instead if a random sample is chosen then the sample would make sure that it is giving unbiased opinion of the whole class and none of the student is missed as it is random everyone has the same chance of being selected.

Do comment if you have any doubt.

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