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:
In order to avoid unconscious bias, neither the subjects not the doctors who examined them knew whether a particular subject was taking vitamins or dummy pills. This is called
A) the placebo effect.
B) the double-blind technique.
C) the retrospective method.
D) stratified sampling.
E) internal validity.

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: 
In order to avoid unconscious bias, neither the subjects not the doctors who examined them knew whether a particular subject was taking vitamins or dummy pills. This is called
A) the placebo effect. 
B) the double-blind technique. 
C) the retrospective method. 
D) stratified sampling. 
E) internal validity.

Quizplus · Accepted Answer

The study design used the double-blind technique, which involves neither the subjects nor the doctors knowing which group each subject was assigned to. This helps to avoid unconscious bias and ensures that the results are more reliable. The placebo effect refers to the phenomenon where people may experience a perceived benefit from a treatment even if it has no active ingredient. Retrospective method and stratified sampling are not relevant to this study. Internal validity refers to the extent to which a study measures what it intends to measure; while it is important in research, it is not related to the specific method used in this study to avoid bias.

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