Chapter 6, Problem 6.75RE

(a)

To determine

To explain what are the explanatory and response variables in this study.

Explanation of Solution

The explanatory variable was whether or not the patients were treated with surgery. The response variable is how long the patients lived after treatment.

(b)

To determine

To explain is this study an experiment why or why not.

Answer to Problem 6.75RE

Yes.

Explanation of Solution

This study is an experiment because a treatment, whether or not a patient receives surgery, is present.

(c)

To determine

To explain why the conclusion of the study is not supported by the data.

Explanation of Solution

This new fact means that the patients who did not receive surgery were more ill than those that did receive surgery and just could not receive the surgery. This creates a confounding variable since this implies that it is the severity of the cancer, and not whether or not the patient was treated with surgery, that influenced how long the patient lived after treatment.

To determine

(d)

To outline the design of the randomized comparative experiment.

Explanation of Solution

Randomly select a group of patients who are at the same stage of cancer and are all able to receive surgery. Randomly select half of this group to not receive surgery and the other half to receive surgery. Compare how long the patients in each group lived, on average.