Baker’s versus brewer’s yeast. The Electronic Journal of Biotechnology (Dec. 15, 2003) published an article comparing 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), and the autolysis yield (recorded as a percentage) was measured for each of the yeast–temperature combinations.

The goal of the analysis is to investigate the impact of yeast extract and temperature on mean autolysis yield.

a. Identify the factors (and factor levels) in the experiment.

b. Identify the response variable.

c. How many treatments are included in the experiment?

d. What type of experimental design is employed?