A study by Grimstvedt et al. (2010) of the effects of signage on stair use in university buildings examined the effect of placing signs encouraging stair use near elevators. Based on their design, Blake is designing a study for her campus. The initial part of the study will be a month-long measuring of elevator and stair use in four buildings on the campus. This will be followed by the treatment, which is the simultaneous posting of signs at each of the four locations. Elevator and stair use will then be measured for another month. Which type of design is this?