Video racing. A student runs an experiment to test how different factors affect his reaction time while playing video games. He uses a specified race course with random hazards and times how long it takes him (in seconds) to finish 4 laps under a variety of experimental conditions. As factors, he uses three different types of Mouse (cordless ergonomic, cordless regular, or corded) and keeps the Lights on or off. He measures his time once at each condition. To avoid a learning effect, he runs the race 5 times before selecting the conditions in random order.

a) What are the null and alternative hypotheses for the main effects?

b) How many degrees of freedom does each factor sum of squares have? How about the error sum of squares?

c) Should he consider fitting an interaction term to the model? Why or why not? How many degrees of freedom would it take?