Scientists who are studying a new skin lotion formula plan to compare dryness of skin for people who use the new formula with the dryness of skin for people who use the current formula. eight volunteers are available to participate in this study. information on these volunteers is shown in the table.

volunteer gender age, year
1 male 23
2 female 25
3 female 51
4 female 24
5 male 27
6 male 53
7 male 52
8 female 56
part a: these scientists want to conduct an experiment involving the two formulas (new and current) of lotion. they think skin dryness changes based on age, but not gender. create four blocks of two volunteers (because there are two treatments) and identify the volunteers by number that would be included in each block. provide the criteria you used to determine the blocks. (3 points)

part b: another set of scientists believes skin dryness changes based on both age and gender. these scientists are also using four blocks of two volunteers for each block. identify the volunteers, by number, to be included in each of the four blocks and give the criteria you used to form the blocks. (3 points)

part c: the scientists in part b decide to select two of the four blocks to receive the new formula and to give the other two blocks the current formula. is this an appropriate way to assign treatments? if so, describe a method for selecting the two blocks to receive the new formula. if not, describe an appropriate method for assigning treatments.