Difficulty: Easy

Average Score: 100%

A student notes that ferns outside of his home grow at the same relative rate. After seeing an advertisement for a miracle fertilizer that will help plants grow 'faster than ever,' he wonders if they will help his ferns grow faster too. He approaches the experiment with the hypothesis that fertilizer will help his ferns grow faster.

An appropriate control for his experiment would be

Rationale

A fern in a pot of soil with no fertilizer is the appropriate control for the experiment.

In scientific experiments, a control is a standard against which the results of the test are compared. It is a group or sample that receives no treatment and is used to verify that the experimental conditions themselves did not cause the results observed in the experimental group.

A (a fern in a pot of soil with a minimal amount of fertilizer) YOUR ANSWER

This choice is not the best control for the experiment because it is not devoid of the independent variable, which in this case is the fertilizer. A control group should not be exposed to the experimental treatment. This helps to ensure that any observed differences are due to the treatment alone and not some other variable.

B (a fern in a pot of soil with a large amount of fertilizer) YOUR ANSWER

This choice is incorrect because it is not devoid of the independent variable (fertilizer). It would not serve as a proper control because it exposes the fern to the treatment, which the control group should avoid to ensure that any differences observed are due to the treatment alone.

C (a fern in a pot of soil with no fertilizer) CORRECT

This is the correct answer. A control group in an experiment is the group that does not receive the variable being tested, in this case, the fertilizer. By comparing the growth rate of ferns with and without fertilizer, the student can accurately determine the effect of the fertilizer on the growth rate of the ferns.

D (a fern in a pot with nothing but fertilizer) YOUR ANSWER

This choice is incorrect because it does not provide a suitable control. It is an extreme condition that does not represent a normal growing condition for the ferns. Furthermore, this choice includes the independent variable (fertilizer), which should not be present in the control group.

Conclusion

In a scientific experiment, the control group is essential to validate the results of the study. In this case, a fern in a pot of soil with no fertilizer serves as the control for the experiment, allowing the student to compare the growth rates of ferns with and without fertilizer. This comparison will enable the student to accurately determine whether the fertilizer has any effect on the growth rate of the ferns.

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