The results of a scientific poll showed that 64 out of 400 patients at a certain hospital are not satisfied with the care they received in the hospital after major surgery. A consumer advocate claims that 20% of the surgery patients at a major hospital are dissatisfied with after-surgery care. If the advocate's claim is true, meaning that the true proportion of dissatisfied patients is p=0.20, what is the chance that for a random sample of 400 patients, the sample proportion of dissatisfied patients is less than 0.16?