Answer:
Voluntary response sample
Explanation:
They constitute voluntary response sample. Voluntary response sample is a sample that is made up of volunteers.
Apart from voluntary response sample, it can also be called or known as self-selected sample.
A good example of this sample is the typical phone in polls u can witness on radio or tv stations where people call to air their views or make their stands known.
The voluntary response sample is most times chosen or selected by the people that will respond rather than the administrator of the survey.
One of the standout advantages or benefit of the voluntary response sampling is the convenience and probably the ethical considerations as well. The demerit is that this self-selected samples are sometimes subject to bias.