Chapter 4.2, Problem 78E

(a)

To determine

To find out which are the blocks in this experiment: the cancer therapies or the two sexes and why.

Answer to Problem 78E

The blocks are the gender of the patients.

Explanation of Solution

In this question an experiment was conducted in which the patients were male or female while they were randomly assigned to a therapy for treatment. Since the therapies are not characteristics of patients itself the therapies cannot be blocks for the patients as they were randomly assigned to the treatments. Thus, the blocks cannot be the treatments but have to be the characteristics of the patients and thus the gender have to be the different blocks as the gender of a subject is a characteristics of the subject. Therefore, the blocks are the gender of the patients: male or female.

(b)

To determine

To explain what are the advantages of a randomized block design over a completely randomized design using these $\text{800}$ subjects.

Explanation of Solution

In this question an experiment was conducted in which the patients were male or female while they were randomly assigned to a therapy for treatment. And the blocks are the gender of the patients: male or female. Thus, a random block design can group the subjects into blocks which have a common characteristics and thus a randomized block design allows us to take into account the change of one or more extra variables. A completely randomized design is only able to take into account the changes of the predictor variables.

(c)

To determine

To explain what advantages would this offer and what disadvantages are there.

Explanation of Solution

In this question an experiment was conducted in which the patients were male or female while they were randomly assigned to a therapy for treatment. And the blocks are the gender of the patients: male or female. Suppose the researchers had $\text{800}$ males and no females subjects available for the study then the advantages would this offer is that researchers can fixate on whether the drug is working in the males or not. And the disadvantage of this is that this makes it a non-block study and it is now impossible to determine if the drug works for all mankind or just males.