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A company produces and tests a new mineral supplement designed to prevent the common cold. The company tests three dosages of the mineral supplement on 300 participants, male and female, between the ages of 25 and 50, over a 6-month period. Each group has 100 randomly assigned participants. The table shows the dosages of the mineral supplement given to each participant in each group and the numbers of participants that report having the common cold during the 6-month period.

Mineral Supplement Study

\begin{tabular}{|c|c|c|}
\hline
Group & Dosage & \begin{tabular}{c}
Number of Common \\
Cold Cases
\end{tabular} \\
\hline
1 & [tex]$50 \, \text{mg/day}$[/tex] & 10 \\
\hline
2 & [tex]$100 \, \text{mg/day}$[/tex] & 6 \\
\hline
3 & [tex]$150 \, \text{mg/day}$[/tex] & 5 \\
\hline
\end{tabular}

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 [tex]$200 \, \text{mg/day}$[/tex] of the mineral supplement.



Answer :

GinnyAnswer
To address the issue and resolve the claim, let's consider each of the provided options:

A. Test a fourth group, in which participants do not receive the mineral supplement.

- This option introduces a control group that receives no dosage of the mineral supplement. Having a control group is a crucial part of scientific research because it allows for comparison with the test groups. This helps determine if the effects observed in the test groups are genuinely due to the supplement or other factors. By comparing the common cold incidence in the control group with those in the supplement groups, the efficacy of the supplement can be assessed more accurately.

B. Test all three groups, with each participant receiving the mineral supplement for 12 months.

- Extending the testing period to 12 months could provide more data on the long-term effectiveness of the supplement. However, this change does not address the need for a control group. Without a control group, it's challenging to attribute the reduced common cold cases directly to the supplement rather than other variables such as seasonal changes, participants' varying health conditions, or placebo effect.

C. Test only one group, with each participant receiving [tex]$200 mg /$[/tex] day of the mineral supplement.

- This option changes the dosage and reduces the number of test groups to one. However, testing only one group removes the comparative aspect essential in an investigation. Without multiple dosages and a control group, it's impossible to understand the dosage effectiveness or compare the results against a baseline without supplementation.

Among these options, Option A is the most appropriate solution as it would remove the source of the error. Introducing a control group ensures that there is a valid baseline to compare the incidence rates of the common cold, thereby validating or refuting the claim of the supplement's effectiveness based on evidence.

Therefore, the correct answer is:
A. Test a fourth group, in which participants do not receive the mineral supplement.

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