14.71 Three factors An experiment analyzed how the mean corn yield depends on three different fertilizers:

Nitrogen (applied at low and high levels), phosphate

(applied at low and high levels), and potash (applied at low and high levels). In the experiment, each plot of land received a combination of levels from these three fertilizers.

a. How many groups result from the different combinations of the three factors?

b. Defining indicator variables, state the regression model that corresponds to an ANOVA assuming a lack of interaction.

c. Give possible estimates of the model parameters in part b for which the estimated corn yield would be highest at the high level of nitrogen fertilizer and phosphate fertilizer and the low level of potash.

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