Do Doctors in Managed-Care Plans Give Less Charity Care? Researchers

Do doctors in managed-care plans give less charity care? Researchers chose 60 communities at random and then chose doctors at random in each community. In all, they interviewed 10,881 doctors. Overall, 77.3 percent of the doctors said they had given some care free or at reduced rates because of the patient's financial need in the month before the interview. Doctors who received at least 85 percent of their practice income from managed-care plans were significantly less likely than other doctors to provide charity care.
The number 77.3 percent is:

A) a statistic because it describes a sample.
B) a statistic because it describes a population.
C) a parameter because it describes a sample.
D) a parameter because it describes a population.