Matching?

Researchers randomly select four of the twenty-one US federal penitentiaries and then randomly select correctional staff to participate in a study on how work settings influence behavior.
	Prison staff provide a list of new inmates entering the prison each week, and researchers use a program that chooses without bias who from the list to ask to participate in their study.
12345678	The warden at the prison tells the researcher that prisoners who make the "good behavior" list for the week can participate in the researcher's study.
12345678	At the prison, the researcher randomly selects cell blocks and then samples every inmate within that cell block.
12345678	The researchers are given permission to come to the prison for a period of two weeks, during which time they interview whichever prisoners agree to participate. They interview until they have collected data from 20 inmates who are serving sentences that are shorter than a year, 20 who are serving 1 to 3 years, and 20 who are serving more than 3 years.

1.	Simple random sampling
2.	Convenience
3.	Systematic sampling
4.	Snowball sampling
5.	Cluster sampling
6.	Quota sampling
7.	Multistage sampling
8.	Stratified Random Sampling