Explanation
This question is about evaluating which additional piece of information would most strengthen the researchers' conclusion that a genetic defect increases the likelihood of herniated disks.
A. If 80 out of 100 people without the defective gene still had herniated disks, it would weaken the conclusion that the gene increases the risk, not strengthen it.
B. Finding only 2 out of 100 people with the defective gene having herniated disks does not provide strong support for the conclusion, as it shows a low incidence rate among those with the gene.
C. (Correct Response) If all 30 family members who also had the defective gene suffered from herniated disks, it would significantly strengthen the conclusion by showing a direct correlation within a specific gene pool.
D. This would actually counter the researchers' conclusion by showing a group with herniated disks but no genetic defect, suggesting that the defect is not necessary for the condition.
E. This information suggests that the genetic defect is not present in all cases of herniated disks and does not necessarily support the conclusion that the defect increases the risk.
The option that most strengthens the researchers' conclusion is option C, as it provides strong evidence of a hereditary pattern that correlates the presence of the genetic defect with the occurrence of herniated disks.