Non-probability: Availability

The sample selection is based on the units' accessibility/relative ease of access. They may be easy to approach, or may themselves choose to participate in the study (self-selection). Researchers may have particular target groups in mind but they do not control the sample selection mechanism. For example, students leaving a particular building on campus may be approached, or individuals may volunteer to participate in response to invitations that do not target them specifically, but a larger group to which they may belong. Also called "convenience" or "opportunity" sampling.