3.16 What is wrong? Explain what is wrong with each of the following randomization procedures and describe how you would do the randomization correctly.

a. Twenty subjects are to be assigned to two treatments, 10 to each. For each subject, a coin is tossed.

If the coin comes up heads, the subject is assigned to the first treatment; if the coin comes up tails, the subject is assigned to the second treatment.

b. An experiment will assign 50 rats to five different treatment conditions. The rats arrive from the supplier in batches of 10, and the treatment lasts two weeks. The first batch of 10 rats is randomly assigned to one of the five treatments, and data for these rats are collected. After a one-week break, another batch of 10 rats arrives and is assigned to one of the four remaining treatments. The process continues until the last batch of rats is given the treatment that has not been assigned to the four previous batches.

c. Thirty students are to be used to evaluate a new treatment. Fifteen women are assigned to receive the treatment, and 15 men are assigned to be the controls.