Medical professionals need to know the absorption rate of caffeine in the bloodstream. In a study of the relationship between caffeine intake (in milligrams) and absorption (in parts per million) by...

Medical professionals need to know the absorption rate of caffeine in the bloodstream. In a study of the relationship between caffeine intake (in milligrams) and absorption (in parts per million) by the bloodstream, scientists computed the regression of caffeine and absorption rate.  The 12 volunteers used in the study were given caffeine tablets with as few as 216 mg and as many as 410 mg.  Absorption rates ranged from 3600 ppm to 7800 ppm. Some computer output from a regression analysis of these data is shown below.

1. a) What is the equation of the least squares regression line that describes the relationship between caffeine intake and absorption in the bloodstream? Define any variables used in this equation.

1. b) What is the value of the correlation coefficient for caffeine intake and absorption rate? Interpret this correlation.

1. c) Suppose that you want to describe the relationship between caffeine intake and absorption rate only in the range of 250 to 350 milligrams. Does the line shown in the scatterplot still provide the best description of the relationship for the data in this range? Why or why not?

Extracted text: SCATTERPLOT WITH LEAST SQUARES REGRESSION LINE 8000 7000 6000 5000 4000- 200 300 400 Caffeine (in milligrams) StDev 1226 4.027 Predictor Coef T Constant Caffeine 0.93 3.64 1136 0.376 14.673 0.005 S= 845.3 R-Sq = 57.0% R-Sq (adj) = 52.7% Parts Per Million