A Health Psychologist Was Interested in the Effects of Smoking

A health psychologist was interested in the effects of smoking on the suppression of the immune system. Three groups of adults were exposed (in a highly ethical way) to either a cold virus, a flu virus or were left freezing wet in the outside in the middle of winter to catch pneumonia (no more than smokers deserve!) . The severity of the disease was then measured as a percentage (0% = not contracted, 100% = contracted to a very severe degree) . The psychologist also measured the number of cigarettes that each person smoked per day. The psychologist was interested in the differences in the severity of the three illnesses and the impact of cigarette usage. What technique should be used to analyse these data?

A) Two-way repeated-measures ANOVA.
B) Two-way independent ANOVA.
C) Two-way mixed ANOVA.
D) One-way analysis of covariance.