Doctors and nurses. Nurse practitioners are nurses with advanced qualifications who often act much like primary care physicians. An experiment assigned 1316 patients who had no regular source of medical care to either a doctor (510 patients) or a nurse practitioner (806 patients). All of the patients had been diagnosed with either asthma, diabetes, or high blood pressure before being assigned. The response variables included measures of the patients' health and of their satisfaction with their medical care after 6 months.
(a) Is the diagnosis (asthma, etc.) a treatment variable or a block? Why?
(b) Is the type of care (nurse or doctor) a treatment variable or a block? Why?