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. Why is randomization important when setting up an experiment to answer this research question?

to ensure that both groups have a nice mix of students
to ensure that the two groups have the same number of students
to ensure that both groups are roughly equivalent regarding students’ preparedness, anxiety levels, and study skills
to ensure that the rooms for both groups are approximately the same regarding time of day, temperature, sound control, and lighting
A researcher wants to know if eating a mint affects whether people can distinguish between two popular orange juice brands. To conduct an experiment, the researcher places participants in two groups. The treatment group will eat a mint before drinking a juice, while the control group will not eat a mint before drinking. Then the participants will guess the juice brand.

Randomization is important when assigning the participants to the treatment and control groups to ensure

that there will be the same number of participants in both groups.
that the experiment results can be generalized to all people.
that both groups have participants that like both popular juice brands.
that both groups are roughly equivalent with regards to demographics and juice preferences.