John Hoogland studied alarm calls in black-tailed prairie dogs in the Black Hills of South Dakota. Prairie dogs are large squirrels that live in family groups called coteries. Each coterie has its own territory inside a prairie dog town. Prairie dogs have many predators and spend a lot of their time on alert. When a predator is spotted, a prairie dog will often sound an alarm with high-pitched barking.This brings attention to the caller putting it at higher risk of predation, but the other prairie dogs scatter to safety underground. Hoogland suspected this altruistic behavior was due to kin selection - by protecting nearby relatives, they are protecting shared genes. To test this, he and his assistants pulled a stuffed badger on a sled through a prairie dog town and then recorded which individuals called and whether their relatives were nearby when they called. The results are in the graph below. In this experiment, the "Percentage of simulated badger attcks in which prairie dogs gave alarm calls" is the ____. independent/explanatory variable experiment group dependent/response variable standardized variable control group