The following data on concentration (g/L) and time (days) for a particular blend of malt liquor was read from a scatter plot in the article “Improving Fermentation Productivity with Reverse Osmosis” (Food Tech., 1984: 92–96):

x 1 2 34 56 7 8 y 74 54 52 51 52 53 58 71

a. Verify that a scatter plot of the data is consistent with the choice of a quadratic regression model.

b. The estimated quadratic regression equation is

. Predict the value of glucose concentration for a fermentation time of 6 days, and compute the corresponding residual.

c. Using , what proportion of observed variation can be attributed to the quadratic regression relationship?

d. The standardized residuals based on the quadratic model are 1.91, 1.95, .25, .58, .90, .04, .66, and

.20. Construct a plot of the standardized residuals versus n 5 8 SSE 5 61.77 y 5 84.482 2 15.875x 1 1.7679x 2 x 5 fermentation y 5 glucose S 5 10.15 R-Sq 5 93.8% R-Sq(adj) 5 89.6%

bulkdens 5 403 1 16.2 moiscont 2 0.706 contsqd x and a normal probability plot. Do the plots exhibit any troublesome features?

e. The estimated standard deviation of —that is,

—is 1.69. Compute a 95% CI for .

f. Compute a 95% PI for a glucose concentration observation made after 6 days of fermentation time.