Self-study
Vitamin XYZ has long been a favorite among health food enthusiasts. ██ █ ██████ █████ ██████ █████ ███ ████ █████ ███████ ██ ███████ ███ █████ ███ ███ █████ ██████ ██ ███████ █ ██ ███████ █████ ████ ██ █████ ███████ ████ ███ ███████ ██ █ ███████ ██████ ███████████ █████████ ███ ███████████ ██ ████████ ██████ ███████ ████ ██ █████
Stimulus Breakdown
The stimulus tells us about a recent large study concerning vitamin XYZ. The study had an experimental group who took large doses of vitamin XYZ daily for two years, and a control group who did not take vitamin XYZ. Researchers also accounted for relevant differences between participants, such as diet. At the end of the two years, the experimental group who took vitamin XYZ had a 40% lower average risk of heart disease than the control group.
When considering the results from an experimental study, it's important to consider the quality of the study. And this study looks pretty good: it included a large number of participants and a control group, and researchers controlled for confounding factors that could have raised alternative explanations.
Objective: Identify a Strongly-Supported Claim
Because the study presented in the stimulus was of good quality, we can reasonably infer that vitamin XYZ actually caused the lower average risk of heart disease. This claim is strongly supported by the way the study was conducted to eliminate possible alternative explanations.
11.
Which one of the following ██████████ ██ ████ █████████ ██ ███ ████████
a
Taking large amounts ██ ████████ ██ ████████ █████ ███████ ███ ████ ████████
The stimulus only discusses vitamin XYZ, not vitamins in general. It's also limited to the effect of vitamin XYZ on heart disease, and doesn't say anything about the overall cost/benefit of taking vitamins. (A) goes beyond the scope of the stimulus.
b
Those who take █████ █████ ██ ███████ ███ █████ ███ ███ ████ ███ █████ ████ ███████ ██ ███████ ██ ████████ ██ ███ ██████████ ██ ████████ █████ ████████
(B) takes our reasonably inferred conclusion of the study one step further. The study strongly supports concluding that taking large doses of vitamin XYZ for two years reduces the average risk of heart disease, so we can predict the same result in the future.
c
Li, who has █████ █████ ███████ ██ ███████ ███ █████ ███ ███ ████ ███ ██████ ███ █ ██ ███████ █████ ████ ██ █████ ███████ ████ ███ ███ ███ █████ ████
Because the study only talks about average effects across a large group of people, it can't support predictions about a specific individual. There are too many other factors in any individual case: for example, Lin might have made other lifestyle changes that could outweigh the effects of vitamin XYZ.
d
Taking large amounts ██ ███████ ███ █████ ████ ███ ██████ ██ █████ █████ ████ ██████ ██ ███████████ ██ ████ ███████
The study is limited to the effect of vitamin XYZ on heart disease over two years. We don't know if vitamin XYZ has undesirable side effects, continues to be effective over a longer period, or any other information we'd need to support (D).
e
Health food enthusiasts ███ ████████ ███████ ██ █████████ ████ █████ █████ █████ ██ ████████ ████████ ███████ ████ ███████
(E) has the same issue as (A) and (D): it goes beyond the scope of the stimulus. We can't support a claim about multiple vitamins promoting general good health just based on a study about vitamin XYZ lowering the risk of heart disease.