Daily Two-Mile Walk Halves Death Risk: Between 1980 and 1992, researchers studied765nonsmoking, retired men, aged 61 to 81 years, and collected mortality data on these men over the following 12 years. During the study,205of the men died. The study results show that while51.2%of men who walked less than one mile per day died, only half this figure-25.5%-of the men who walked more than two miles per day died.

Refer to the headline in this study and to the statement "While51.2%of the men who walked less than one mile per day died, only half this figure-25.5%-of the men who walked more than two miles per day died."

(a) What two categorical variables measured on each participant are used in making that statement? (Select all that apply.)

1. amount walked per day
2. whether the man died during the study
3. duration of the experiment
4. number of participants
5. number of deaths