Arepresentative for mrs. jones donuts stood outside of a grocery store with a clipboard, a survey form, and a table filled with donuts and small glasses of milk. the sign on the table said "free donuts." after each person picked up a donut and took a bite, she would ask, "isn't that good? " each positive reply, even if it was just a nod of the head, was entered on her clipboard sheet as a preference for that kind of donut. what kind of sampling is this?