Sample Designs
A nonprobability sample relies on personal judgment and prohibits estimating the probability that any member of the population will be included in the sample. Nonprobability samples can be classified as convenience, judgment, or quota.
 | A convenience sample is sometimes called an accidental sample. Those included in the sample just happened to be where the study was being conducted at the time it was being conducted. |
| A judgment sample is sometimes called a purposive sample. Those included in the sample are chosen because the researcher believes that they will be good prospects for accurate information. |
| A quota sample is a prescribed number of people possessing a certain characteristic, which is approximately the same proportion of the people with the characteristic in the population. |
In a probability sample, each member of the population has an equal chance of being
included in the sample. Probability samples can be classified as simple random,
stratified, or cluster.
| A simple random sample means that every member of the population has a known and equal chance of selection. |
| A stratified sample divides the parent population into mutually exclusive and exhaustive subsets. Then, random samples are drawn from each subset or group. |
| A cluster sample divides the parent population into mutually exclusive and exhaustive subsets. Then, a random sample of subsets is selected. |
Copyright © 1999 by Gemmy Allen, all rights reserved.