A study is conducted to determine if the blue light from a tablet device will affect the fall asleep time of people in various age groups differently. Volunteers for the study are grouped by age: 18-30, 31-50, and 50. Half of each group is assigned a standard tablet, the other half is assigned a tablet with reduced blue light. People in each group are asked to use the tablet for 10 minutes before bed and their fall asleep time is recorded. Which of the following is correct?
a. Blocks: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: How the eyes react to blue light.
b. Blocks: the three age groups. Treatments: measuring how long it takes to fall asleep. Response variable: The hours of sleep recorded.
c. Strata: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: How the eyes react to blue light.
d. Blocks: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: Time it takes to fall asleep.
e. Blocks: the group receiving the standard tablet and the group receiving the reduced blue light tablet. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: Time it takes to fall asleep.