Hair color and pain. Studies conducted at the University of Melbourne (Australia) indicate that there may be a difference between the pain thresholds of blondes and brunettes. Men and women of various...

Hair color and pain. Studies conducted at the University of Melbourne (Australia) indicate that there may be a difference between the pain thresholds of blondes and brunettes. Men and women of various ages were divided into four categories according to hair color: light blond, dark blond, light brunette, and dark brunette. The purpose of the experiment was to determine whether hair color is related to the amount of pain evoked by common types of mishaps and assorted types of trauma. Each person in the experiment was given a pain threshold score based on his or her performance in a pain sensitivity test (the higher the score, the higher the person’s pain tolerance). SAS was used to conduct the analysis of variance of the data listed in the table. The SAS printout is also provided (top, p. 702).

(a) Based on the given information, what type of experimental design appears to have been employed?

(b) Using the SAS printout, conduct a test to determine whether the mean pain thresholds differ among people possessing the four types of hair color. Use α = .05.

(c) What is the observed significance level for the test in part b? Interpret it.

(d) What assumptions must be met in order to ensure the validity of the inferences you made in part b?