A researcher wants to study people who have a rare disease u…

A researcher wants to study people who have a rare disease using interview techniques. This researcher asks a friend who has this disease if she would consent to an interview. Then the researcher asks this friend if she could name other people having the same disease. This friend provides the researcher with five names. The researcher contacts those five people, interviews them, and asks each for names of people with this disease. This sampling technique is known as