In a hypothetical study of people taking daily multi-vitamin supplements, the following data was obtained to determine the impact of multi-vitamin intake on the overall risk reduction for developing cancer. The results of the study indicated that the incidence of cancers was 15% in the people who took multi-vitamin supplements regularly versus 30% in people who did not take multi-vitamins.

a. Calculate the preventive fraction. b. Interpret the PF you calculated in letter a in language that the public will understand.