Explain the roles of sample, control, and replication in experimental design.

• A. A sample is the entire population; a control is a random subset; replication repeats measurements to confirm accuracy.
• B. The control group receives extra food to ensure they perform better.
• C. Replication refers to testing multiple times to estimate variability.
• D. Sample is a subset of the population; a control provides a baseline; replication repeats trials to estimate variability and reliability.

Answer: (D)

In experimental design, the roles of sample, control, and replication are about how you study a bigger population in a reliable, interpretable way. A sample is a subset of the population you actually study, not the whole group. A control provides a baseline condition to compare against the experimental treatment, helping you isolate the effect of the variable you’re testing by keeping other factors constant. Replication means repeating trials or measurements to capture natural variability and to estimate how reliable or precise your results are.

That matches the statement describing a sample as a subset of the population, a control as a baseline, and replication as repeating trials to estimate variability and reliability. The other options misunderstand these roles: one wrongly says the sample is the entire population and that a control is a random subset, another attributes the control to receiving extra food, and another only mentions replication without defining sample and control.