Under a certain payment model, government reimbursement to a hospital depends on that hospital's patient satisfaction scores. Heather is overseeing an internal quality control survey, in which a random sample of 100 patients is taken. Among other variables, the patients are asked if they are satisfi ed with the care they received, as a yes/no response. Assume that the patients are unrelated, and that the potential patient pool is very large. Also assume that the true patient satisfaction rate at Heather's hospital is 80%.

What is the variance of the number of satisfied patients?