Question

A new cream was developed to reduce the irritation caused by poison ivy. To test the effectiveness, researchers placed an ad online asking for volunteers to participate in the study. One hundred subjects replied and were informed that one group would receive the new cream and the other group would receive a cream with no active ingredient. All 100 subjects were exposed to poison ivy. Fifty were then randomly assigned to the group with the new cream, and 50 were randomly assigned to the group with the cream with no active ingredient. After three days, the subjects’ level of irritation was measured.

Which of the following accurately describes the benefit of comparison in the experiment?

The overall level of irritation can be compared to see if the new cream had a significant effect.
The level of irritation for both groups can be compared to see if the new cream had a significant effect.
The level of irritation in the treatment group only can be compared to see if the new cream had a significant effect
Since one group received a cream with no active ingredient, the researchers will not be able to determine of the new cream is effective.

Answer 1

The level of irritation for both groups can be compared to see if the new cream had a significant effect.

Explanation:

the phrasing is a bit strange.

but I think the first one means "overall" in the sense of outside and inside the 2 test groups.

the third one would object compare results only inside the group that got the active ingredient.

the 4th one is just nonsense.

so, only the second answer option makes sense. these 2 groups are created so that their results can be compared. that is the whole point.

Answer 2

The level of irritation for both groups can be compared to see if the new cream had a significant effect.

Explanation:

In this experiment, the purpose of having two groups is one being the control group, and one being the group being experimented on. The control group is needed in order to know for sure that it is the cream that is beneficial, instead of an outside factor such as the poison ivy being bad.

By comparing the level of irritation for both groups, it will become apparent if the new cream has a side effect.