Text stimulus (diagram): A two-by-two experimental design grid. Horizontal axis: Shared goal, No on left and Yes on right. Vertical axis: Equal status, No on bottom and Yes on top. Labels: cells Group 1 through Group 4. Under the grid, add a note: 'All groups: 8 weeks, same facilitator training, same meeting time.' What is the main advantage of assigning participants to all four cells while holding duration and staff support constant?