Question

a scientist was asked to test the effect of a new vitamin for rats. his hypothesis was that young rats that had vitamins added to their food would gain weight faster than young rats fed a normal diet. he predicted that if young rats were fed vitamins, then they would gain more weight by the end of the experiment. he tested the effect of adding vitamins to some of the rats diet by measuring the amount of weight each rat gained after three months. he then determined the average weight gained in each group. to analyze his results, he put the data he collected into the table shown below.

what was the control group for this experiment?

a. there was no control group because the rats did not all start at the same weight.

b. the control group was the rats fed the normal diet plus the vitamins.

c. the control group was the starting weights of all the rats.

d. the control group was the rats fed the normal diet without added vitamins.

Explanation:

In an experiment, the control group is the group that does not receive the treatment (in this case, the added vitamins). The group with the normal diet (no vitamins) serves as a baseline to compare against the group that received the treatment (normal diet + vitamins). Option A is incorrect as having different starting weights doesn't mean no control group. Option B is wrong as that's the experimental group (receiving the treatment - vitamins). Option C is incorrect as starting weights are just data points, not a group.

Answer:

D. The control group was the rats fed the normal diet without added vitamins.