A. cluster sample "The population is first split into groups. The overall sample consists of every member from some of the groups. The groups are selected at random." - 16. Samples are randomly selected from representative groups.
B. multi-stage sample - 14. Two or more levels of random sampling are used.
C. voluntary-response (It's voluntary so people decide if they want to participate when they are invited)- 15. The population is invited to respond.
D.convenience sample
"Convenience sample: The researcher chooses a sample that is readily available in some non-random way."
- 13. An easily accessible sample is chosen.