*Haylish had a common cold during the 6-month period.
Mineral Supplement Study
| Group | Dosage | Number of Common Cold Cases |
| :---- | :------------ | :-------------------------- |
| 1 | $50 mg /$ day | 10 |
| 2 | $100 mg /$ day | 6 |
| 3 | $150 mg /$ day | 5 |
The company claims that the mineral supplement can effectively prevent the common cold. A scientist disputes the claim, saying an error exists in the setup of the groups for the investigation. Which change to the investigation would remove the source of this error?
A. Test a fourth group, in which participants do not receive the mineral supplement.
B. Test all three groups, with each participant receiving the mineral supplement for 12 months.
C. Test only one group, with each participant receiving $200 mg /$ day of the mineral supplement.
D. Test only two groups, one with each participant receiving $200 mg /$ day and one with $50 mg /$ day of the mineral supplement.
Answer (2)
The study lacks a control group, which is necessary to determine if the mineral supplement has any effect. Option A introduces a fourth group that does not receive the supplement, serving as a control. Therefore, the answer is A.
Explanation
Identify the Error in the Study Design The primary error in the study design is the absence of a control group. A control group, which does not receive the mineral supplement, is crucial for comparison to determine the true effect of the supplement. Without a control group, it's impossible to tell if the lower number of cold cases in groups receiving higher dosages is due to the supplement or some other factor.
Evaluate Each Option Let's evaluate each option to see which one addresses the need for a control group:
Option A: Test a fourth group, in which participants do not receive the mineral supplement. This option introduces a control group, which is exactly what is needed to validate the study.
Option B: Test all three groups, with each participant receiving the mineral supplement for 12 months. This does not introduce a control group.
Option C: Test only one group, with each participant receiving 200 m g / day of the mineral supplement. This does not introduce a control group.
Option D: Test only two groups, one with each participant receiving 200 m g / day and one with 50 m g / day of the mineral supplement. This does not introduce a control group.
Select the Correct Option Option A is the only option that includes a control group. Therefore, the correct answer is A.
Examples
In medical research, it's crucial to have a control group when testing new treatments or drugs. For example, if you're testing a new drug for headaches, you would give the drug to one group of people and a placebo (a sugar pill with no active ingredients) to another group. By comparing the results, you can determine if the drug is actually effective or if the improvement is just due to the placebo effect. This same principle applies to testing mineral supplements or any other intervention where you want to determine its true impact.
The study's primary flaw is the lack of a control group. Introducing a control group, as suggested in Option A, is essential to accurately assess the effectiveness of the mineral supplement. Therefore, the correct answer is A.
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