Assume that you are asked to help design a study for an owner of four organic grocery stores, each located in a different city. The owner is interested in knowing whether placing an advertisement in the main Sunday paper will promote business (increase total sales) in the stores. You are considering the following three options: no advertisement, offering a coupon for one free item (with purchase), offering a coupon for special prices on a several items. For simplicity, we will assume that each coupon is effective for seven days (Sunday through Saturday). Write a brief outline for an experimental design.
a. Identify any extraneous variables that may potentially bias your results. How will these potential biases be addressed?
b. List the two factors and corresponding levels in your experimental design.
c. Specify the response variable you will use.
d. Specify the units and sample size for this study.
e. List each factor- level combination and the order in which things will be tested at each location. Describe how you determined the order of each factor- level combination.
f. List the factors and the corresponding degrees of freedom that will occur in the ANOVA table.