The following data on y = glucose concentration (g/L) and x = fermentation time (days) for a particular blend of malt liquor was read from a scatterplot in the article "Improving Fermentation Productivity with Reverse Osmosis" (Food Tech., 1984: 92-96):

a. Verify that a scatterplot of the data is consistent with the choice of a quadratic regression model.
b. The estimated quadratic regression equation is y = 84.482 - 15.875x + 1.7679x2. Predict the value of glucose concentration for a fermentation time of 6 days, and compute the corresponding residual.
c. Using SSE = 61.77, what proportion of observed variation can be attributed to the quadratic regression relationship?
d. The n = 8 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 x and a normal probability plot. Do the plots exhibit any troublesome features?
e. The estimated standard deviation of µÌ‚Y.6-that is, β̂0 + β̂1(6) + β̂0 + (36)-is 1.69. Compute a 95% CI for µY.6.
f. Compute a 95% PI for a glucose concentration observation made after 6 days of fermentation time.

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