Definition of Terms
Target population * the population we want to study
Sampled population * the population from where we actually select the sample
Sample
* these are the elements from the sampled population who are actually selected to participate or to be the subject in the study
Sample size * Total number of elements in the sample
SAMPLING
* the process of selecting a small number of elements from a larger defined target group of elements such that the information gathered from the small group will allow judgments to be made about the larger groups
SAMPLING TECHNIQUES * PROBABILITY SAMPLING a method of selecting a sample wherein each element in the population has a known, nonzero chance of being included in the sample.
Simple Random Sampling a probability sampling method wherein all members of the population have equal chances of being included in the study.
When to use: * If the members of the population are not so spread geographically. * If the members are homogeneous with respect to the characteristic under study. Systematic Sampling probability sampling method wherein the selection of the first member (random start - r) is at random (using simple random sampling) and the selection of the other members in sample is systematic by successively taking every kth member from the random start, where k is the sampling interval.
When to use: * If the arrangement of the members is according to magnitude. * If there is no available list of members of the population.
Stratified Sampling * a probability sampling method where we divide the population into nonoverlapping subpopulations or strata and then select sample (using simple random sampling or systematic sampling) from each stratum based on a stratification variable. The sample consists of all the samples in the different