An article in the Journal of Quality Technology (Vol. 13, No. 2, 1981, pp. 111-114) describes an experiment that investigates the effects of four bleaching chemicals on pulp brightness. These four chemicals were selected at random from a large population of potential bleaching agents. The data are as follows:
(a) Is there a difference in the chemical types? Use a = 0.05.
(b) Estimate the variability due to chemical types.
(c) Estimate the variability due to random error.
(d) Analyze the residuals from this experiment and comment on model adequacy.
