What is a voluntary response sample?

Suppose there is a group of people. There are 500 people in the group. They want to fill out a form and mail it to a certain address. They give the firm and address to each and everyone of the 500 people, but let's say that 300 of the people decide or to do it. Only 200 entries... This is voluntary response sampling. Instead of you asking he people their opinions, they give it to you. (Usually by a survey, form, etc. ) Hope this helped...