13.66 The article “Improving Fermentation Productivity with Reverse Osmosis” (Food Technology [1984]:

92– 96) gave the following data (read from a scatterplot)

on y 5 glucose concentration (g/L) and x 5 fermentation time (days) for a blend of malt liquor.

x 1 2 3 4 5 6 7 8 y 74 54 52 51 52 53 58 71

a. Use the data to calculate the estimated regression line.

b. Do the data indicate a linear relationship between y and x? Test using a .10 significance level.

c. Using the estimated regression line of Part (a), compute the residuals and construct a plot of the residuals versus x (that is, of the (x, residual) pairs).

d. Based on the plot in Part (c), do you think that the simple linear regression model is appropriate for describing the relationship between y and x? Explain.