A random sample of patients who attended a clinic was selected. The age of the patient (years) and the number of days since the last visit were collected and are displayed in the figure below. The least-squares regression line for predicting number of days since the last visit from the age of the patient is y = 600.081 - 8.694x. The slope of this line tells us the
A) correlation between age of patient and days since last visit.
B) change in days since last visit for each year older a patient is, on average.
C) change in the age of the patient for each extra day since the last visit.
D) average days since last visit for all of the patients.

Question

A random sample of patients who attended a clinic was selected. The age of the patient (years) and the number of days since the last visit were collected and are displayed in the figure below. The least-squares regression line for predicting number of days since the last visit from the age of the patient is y = 600.081 - 8.694x.  The slope of this line tells us the
A) correlation between age of patient and days since last visit. 
B) change in days since last visit for each year older a patient is, on average. 
C) change in the age of the patient for each extra day since the last visit. 
D) average days since last visit for all of the patients.

Quizplus · Accepted Answer

The slope of the least-squares regression line represents the average change in the dependent variable (number of days since last visit) for every one-unit increase in the independent variable (age of patient), holding all other variables constant. In this case, the slope is -8.694, indicating that for every one year increase in patient age, there is an average decrease of 8.694 days since their last visit. Therefore, choice B is the correct answer.

A Random Sample of Patients Who Attended a Clinic Was