How to Experiment Well
Assignment
Active
Assigning Treatment Groups
A beauty product company conducts a study to test the effectiveness of a new shampoo to control split ends. One
hundred subjects have volunteered to take part in the study, and will be split into a treatment group and a placebo
group. The study leader will assign the subjects to the groups randomly using slips of paper. Which reason identifies
why randomization is important?
It is important to make sure that groups have 50 people each.
It is important to make sure that the first 50 people to volunteer are not all in the same group.
It is important to make sure that people who do not currently have many split ends are placed in the placebo
group.
It is important that subject characteristics such as hair length, hair color, and gender are distributed equally
among the treatment groups.