Chapter 3.1, Problem 2E

To determine

To find: the explanatory and response variables and explain whether they are categorical or quantitative

Explanation of Solution

Given: Treating breast cancer

Consider a study of treating breast cancer performed by a medical center to determine which of the given two treatments is most effective. The purpose of either procedure is to prolong the life of the patient.

The study will certainly record the survival time of each patient. This really is the outcome of the study: survival time is the response variable. Now, each patient will get one of the two types of treatments; this is a second variable. Let’s call it the “Procedure” variable; it takes one of two possible values, Treatment 1(removal of the breast) and Treatment 2(remove only the tumor and nearby lymph nodes). The entire purpose of the study is to determine how, if at all, the treatment affects survival time.

Type of treatment is an explanatory variable. Type of treatment (explanatory variable or predictor) is used to identify survival time (response or predicted variable). Here, the dependent variable is survival time and the independent variable is treatment. After the explanatory, the response is measured.