Question: Consider the regression model fit to the nisin extraction data in Exercise 12-18. (a) What proportion of total variability is explained by this model? (b)
Consider the regression model fit to the nisin extraction data in Exercise 12-18.
(a) What proportion of total variability is explained by this model?
(b) Construct a normal probability plot of the residuals. What conclusion can you draw from this plot?
(c) Plot the residuals versus y and versus each regressor, and comment on model adequacy.
(d) Calculate Cook€™s distance for the observations in this data set. Are there any influential points in these data?
Exercise 12-18
An article in Biotechnology Progress (2001, Vol. 17, pp. 366€“368) reported on an experiment to investigate and optimize nisin extraction in aqueous two-phase systems (ATPS). The nisin recovery was the dependent variable (y). The two regressor variables were concentration (%) of PEG 4000 (denoted as x1 and concentration (%) of Na2SO4 (denoted as x2). The data are in Table E12-10.
y X1 X2 62.8739 13 11 11 15 76.1328 13 13 87.4667 15 13 102.3236 76.1872 14 12 77.5287 14 12 14 12 76.7824 14 12 77.4381 12 14 78.7417
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