A researcher conducted an experimental study where one group of patients was given a new drug for hypertension and another group was given a commonly used diuretic. The blood pressures of both groups were measured at the same times each day for a week. To assign patients to a study group, a number was pulled from a hat by the nurse admitting the patient.

A researcher conducted an experimental study where one group of patients was given a new drug for hypertension and another group was given a commonly used diuretic. The blood pressures of both groups were measured at the same times each day for a week. To assign patients to a study group, a number was pulled from a hat by the nurse admitting the patient. An odd number meant that the patient was assigned to the group that received the new drug; an even number assigned the patient to the group that received the commonly used diuretic