Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer.
The study design looked like this:
The method used to form the groups should appear in the outline at the point marked "Question A." What is this method?
A) Random allocation
B) Voluntary response
C) First come, first served
D) Divide and conquer
E) Stratified sampling

Question

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer.
The study design looked like this: 
The method used to form the groups should appear in the outline at the point marked "Question A." What is this method?
A) Random allocation 
B) Voluntary response 
C) First come, first served 
D) Divide and conquer 
E) Stratified sampling

Quizplus · Accepted Answer

The method used to form the groups is random allocation, as stated in the passage. The men were selected at random to either take vitamin supplements or a dummy pill, which ensures that the groups are balanced and any differences in outcome can be attributed to the intervention (taking vitamins) rather than other factors.

Does Taking Large Amounts of Vitamins Protect Against Cancer? to Study