A researcher would like to investigate whether people suffering from insomnia can be helped by taking yoga classes.She designs an experiment as follows.She will obtain a group of volunteer insomniacs who do not currently practice yoga.Each person's degree of insomnia at the start of the experiment will be evaluated.Volunteers will be randomly assigned to one of three groups.Those in group 1 will practice yoga every day,those in group 2 will practice 3 times per week,and those in group 3 will not practice yoga.At the end of a suitable time period each person's degree of insomnia will again be evaluated.The improvement for the three groups will then be compared.Explain why it is important to assign volunteers to groups at random rather than letting them choose their own group.

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Gursimran Warainch · Accepted Answer

Final Answer : Randomization is important to equalize across the treatments the effects of unknown sources of variation.Without randomization,there is more likely to be bias due to uncontrolled sources of variation.For example,if volunteers were to choose their treatment instead of being randomly assigned,group 1 would probably contain a higher percentage of highly motivated people.These people may be making other positive changes in addition to yoga.If volunteers are randomly assigned,the highly motivated people would be spread more equally across groups.

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