Students in a large statistics class were randomly divided into two groups. The first group took the midterm exam with soft music playing in the background, and the second group took the exam with no music playing. After the exam was completed, a researcher compared deidentified exam scores of the two groups.

Which of the following is the reason this experiment was not blind?

A. The sample sizes in both groups was large.

B. The students knew whether or not music was playing while they were taking the exam.

C. Students were randomized into the two groups.

D. Some of the students may not have studied for the exam.

E. Researchers looked at exam scores for the two groups.

The correct option is (B).

Step-by-step explanation:

In case of a blind experiment the participants are divided into groups: one is the treatment group and the other is a control group.

The treatment group are provided with the treatment whereas the control group is not provided with the treatment instead they are given placebos.

To keep the experiment bias free the participants are not informed of the group they belong.

In this case an experiment is conducted to determine the effect of music on studying.

One groups studies with music whereas the other studies without music.

But here the students know which group they belong as they can hear the music playing in the background. This effects the results of the experiment.

Thus, the experiment is not blind.

The correct option is (B).