Chapter 6.5, Problem 17PS

Solution

$\left(a\right)$

To find: the validity for the researcher’s conclusion.

Given information: A researcher studied the effect of fiber supplements on heart disease. She identified $175$ people who take fiber supplements and $175$ people who do not take fiber supplements. She found that those who took the supplements had $19\%$ fewer heart attacks those who did not. She concluded that taking fiber supplements reduces the incidence of heart attacks.

Explain why the researcher’s conclusion may not be valid.

Explanation:

The researcher’s conclusion is not valid because she did not take into account the previous heart condition of the people in the survey.

$\left(b\right)$

To find: The way the researcher could have conducted the study to produce valid result.

Given information: Describe how the researcher could have conducted the study differently to produce valid result.

Explanation:

The researcher could have divided the people into two groups with a similar heart condition. In her study, one group can take supplements and the other group cannot take the supplements. Then, she should take the random sample from both groups and compare the result. In this way, the study would produce a valid result.