II.18. Regression. The equation for the least-squares regression line for the data in Table II.3 is
weight = 133.2 − 6.31 × day
(a) Explain carefully what the slope b = −6.31 tells us about how fast the soap lost weight.
(b) Mr. Boggs did not measure the weight of the soap on Day 4. Use the regression equation to predict that weight.
(c) Draw the regression line on your scatterplot from the previous exercise.