A teacher wants to know if burning a scented candle affects students’ performance on pop quizzes. In the experiment, there will be a treatment group and a control group each taking their quizzes in a room that either does or does not have a scented candle burning. On a randomly chosen day, the first 15 students who arrive to class will be the control group while the last 15 students who arrive will be the treatment group. Which statement best describes the composition of the groups?

The characteristics of the two groups should be roughly equivalent because both groups have 15 students.

The characteristics of the two groups should be roughly equivalent because the students were split into groups on a randomly chosen day.

The characteristics of the two groups might not be roughly equivalent because the students were not labeled and given a random number to place them in one of the groups.

The characteristics of the two groups might not be roughly equivalent because students who arrive around the same time might be friends and have similar preferences for scented candles.