a Did the researcher consider other factors that can influence the chance of heart disease?
B
b How can we include other factors in a study?
A
a See solution.
B
b See solution.
Practice makes perfect
a We are given that a researcher wants to study the effect of fiber supplements on heart disease. To do this they chose 175 people who take fiber supplements and 175 people who do not take fiber supplements.
Notice that researcher did not consider other factors that can have an influence on a chance of having a heart disease. We can suspect that people that had some heart problems before can be more likely to have a heart attack no matter whether they take a supplement or not.
Therefore, since the researcher did not take previous heart conditions into account, the researcher's conclusion may not valid.
b As we concluded before, the researcher did not take previous heart conditions into account, which may make their conclusion less valid. To introduce this factor into the study, the researcher could divide the sample based on their supplement consumption and the previous heart conditions.
Previous Heart Problems
No Previous Heart Problems
Fiber Supplementation
Group 1
Group 2
No Fiber Supplementation
Group 3
Group 4
Now, the researcher could select a random sample from each group and repeat the study comparing Group 1 with Group 3 and Group 2 with Group 4. By doing that we could produce more valid results.
