ACT (Enhanced)ScienceEasy
A team of researchers is investigating the effect of a new dietary supplement on muscle growth in athletes. They recruit 100 participants and randomly assign them to two groups. Group A receives the new supplement daily, while Group B receives a placebo. Both groups follow the same training regimen and diet. After 12 weeks, the researchers measure the increase in muscle mass for each participant. What is the most appropriate conclusion if Group A shows significantly greater muscle mass increase than Group B?
- AThe placebo effect caused muscle growth in Group B.
- BThe training regimen is effective for muscle growth.
- CThe diet followed by the participants is optimal for muscle development.
- DThe new dietary supplement likely promotes muscle growth.
Show answer & explanationAnswer & explanation
Correct answer: D. The new dietary supplement likely promotes muscle growth.
The experiment is designed to isolate the effect of the supplement. Since all other variables are controlled, a significant difference between the supplement group and the placebo group indicates the supplement's effect.
Why the other options are wrong
- A. While a placebo effect might occur, the question states Group A showed 'significantly greater' increase, implying the supplement had an effect beyond any placebo response in Group B.
- B. The effectiveness of the training regimen cannot be isolated as both groups followed it; it's a constant, not the variable being tested for its effect on the difference.
- C. Similar to the training regimen, the diet was constant for both groups, so its optimality cannot be determined as the cause of the difference.
Causal Inference
Drawing a conclusion about the cause-and-effect relationship between variables based on experimental results, where confounding variables are controlled.
- Requires a well-designed experiment.
- Involves comparing an experimental group to a control group.
- Aims to isolate the impact of the independent variable.
Memory trick: Isolated variables lead to clear conclusions.