A study of child development measures the age (in months) at which a child begins to talk and also the child's score on an ability test given several years later. The study asks whether the age at which a child talks helps predict the later test score. The least- squares regression line of test score y on age x is y = 110 - 1.3x. According to this regression line, what happens (on the average) when a child starts talking one month later?
A) The test score goes down 110 points.
B) The test score goes down 1.3 points.
C) The test score goes up 110 points.
D) The test score goes up 1.3 points.
E) The test score is 108.7.

Question

Quizplus · Accepted Answer

According to the regression line y = 110 - 1.3x, the coefficient of x is -1.3, which means that for every increase of one unit in x (which represents one month later for the child to start talking), y (test score) decreases by 1.3 units on average. Therefore, when a child starts talking one month later on average, the test score decreases by 1.3 points.

A Study of Child Development Measures the Age (In Months)