The Electronic Journal of Biotechnology (Dec. 15, 2003) published an article on a comparison of two yeast extracts: baker’s yeast and brewer’s yeast. Brewer’s yeast is a surplus by-product obtained from a brewery; hence, it is less expensive than primary-grown baker’s yeast. Samples of both yeast extracts were prepared at four different temperatures (45, 48, 51, and 54°C); thus, a 2 X 4 factorial design with yeast extract at two levels and temperature at four levels was employed. The response variable was the autolysis yield (recorded as a percentage).
a. How many treatments are included in the experiment?
b. An ANOVA found sufficient evidence of factor interaction at α = .05. Interpret this result practically.
c. Give the null and alternative hypotheses for testing the main effects of yeast extract and temperature.
d. Explain why the tests referred to in part c should not be conducted.
e. Multiple comparisons of the four temperature means were conducted for each of the two yeast extracts. Interpret the results, shown as follows:

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