The Academy of Sports Medicine Physicians is interested in determining whether a new training regimen will help long-distance runners improve their performance in marathons. This organization comes to you for some advice on how to design an experiment to test whether this new regimen is more effective than the standard regimen. You have access to a sample of long- distance runners on the track teams at ten different universities. You hope to conduct the experiment over the course of two years because the regimen takes a long time to learn and because you want to include new runners in the sample as they join the track team. You also believe that the effect of the regimen on performance may differ for men and women.