Question

scientists have found that it’s always best to have a control group. why? let’s say you are measuring whether drinking soda makes people smarter. you get a bunch of kids who don’t drink soda, and give them a test. then you have them drink lots of soda for a few weeks and have them take a similar test. you notice that their scores have gone up. wow, did you just prove that soda makes you smarter? not exactly. it could be that those kids had been studying on their own, or learning stuff in school that helped them on the test. a better experiment has a control group. in this case, it would be a second group of kids from the same place whom you test but who don’t drink the soda. if their scores don’t go up, then you’ve just figured out that soda is the real cause.

which of these would provide the best evidence that drinking soda makes people smarter?

a the soda-drinking group does not show improved scores while the control group does.

b the control group’s scores do not improve while the soda-drinking group’s scores do.

c both the control and soda-drinking groups scored exactly the same on the second test.

d the control group scored higher than the soda-drinking group on the first test.

Explanation:

To determine the best evidence that drinking soda makes people smarter, we analyze each option:

• Option A: If the soda - drinking group doesn't show improved scores but the control group does, this suggests that soda does not make people smarter, so A is incorrect.
• Option B: The control group (who don't drink soda) has no score improvement, while the soda - drinking group has score improvement. This follows the logic of a controlled experiment (as explained in the passage, where a control group is used to isolate the effect of the variable, here soda consumption). If the non - soda - drinking group's scores don't go up and the soda - drinking group's do, it is strong evidence that soda is the cause of the score increase (i.e., makes people smarter), so B is correct.
• Option C: If both groups score the same on the second test, it does not show that soda has an effect on making people smarter, so C is incorrect.
• Option D: The initial scores of the two groups do not provide evidence about the effect of drinking soda on intelligence, as we are interested in the change in scores after the soda consumption (or lack thereof for the control group), so D is incorrect.

Answer:

B. The control group's scores do not improve while the soda - drinking group's scores do.