A math instructor asked her students to keep track of how much time each spent studying a chapter on functions in her algebra-trigonometry course. She collected the information together with test scores from that chapter's test. The data are listed in the table below.
Study Time, x (in hours) Test Grade, y (in percent)
23 ............................................. 81%
15 ............................................. 85
17 ............................................. 80
9 .............................................. 75
21 ............................................. 86
13 ............................................. 80
16 ............................................. 85
11 ............................................. 93
(a) Use a graphing calculator to model the data with a linear function.
(b) Predict a student's score if he or she studies 24 hr, 6 hr, and 18 hr.
(c) What is the correlation coefficient? How confident are you about using the regression line to predict function values?