What is one of the most common household toxins, benzene can be found in?

Aresearcher is interested in the effect of exercise on stamina in elderly patients. the patients are randomly assigned to be in a high-exercise or low-exercise training program. at the end of the program, their stamina is measured by seeing how long they can walk comfortably on a treadmill. identify the independent variable. identify the dependent variable and explain how it was measure.