Example 6.1 used

sum(wtlossdat ["B"] *wtlossdat["y"])/4

to compute the main effect of $\mathrm{C}$.a. Explain why the espression is divided by 4 ?

b. Write an $\mathrm{R}$ function to calculate the main effects using the design matrix.

c. Write an $\mathrm{R}$ function to calculate the interaction effects using the design matrix.

Data from Example 6.1

Transcribed Image Text:

Example 6.1. An investigator is interested in examining three components of a weight loss intervention. A. Keeping a food diary B. Increasing activity C. Home visit The investigator plans to investigate all 2x2x2 = 23: = 8 combinations of experimental conditions. The experimental conditions are outlined in Table 6.1. The notation (-,+) is often used to represent the two factor levels in a 2* design. In this case,