The population within a sample is known as a sampling frame, i.e. for example:- a village of 50 individuals, it experiments with a change then it is considered as a sampling frame. The population from which the sampling frame is taken or chosen is known as parent population. The village of 50 individuals, in the above example, is the sampling frame of the population of the district which is known as parent population.
Moreover, one of the important conditions which must be satisfied before entitling a part of the population as a sample is:- the part of the population must have or must follow the same rules, regulation, norms or folkways which the society, as a whole, follows.
The other terms which are used to better understand the sampling methods are the sampling function. The ratio between the size of sampling frame and the size of parent population is known as sampling function. It is also a very important part of this method.
There are two methods of sampling. They are:-
- Purposive sampling
- Probability sampling
A purposive sample is not done randomly. It is a non-probability sample. it is selected on the basis of characteristics of a population, moreover also after analyzing the objective of the study. Purposive sampling is also known as selective sampling. This method selects the individuals of that group which shares same trends, regulations, rules, norms, folkways, and rituals or anything which shall be the target, with the parent group. This type of selection is done with high attention.
A probability sampling method is just opposite to that of the purposive sampling, it is the method of selection is done on a random basis. This method is used to check the acceptability of the change within a society which is not highly diverse. This selection is done when the problem is not within the diversity of society: there are some problems which exist in a society, such society which has the individuals of common interests, in such a situation when a change is proposed then a specified sampling frame is not selected; or in other words probability sampling is used.
Also read, Research Methods and Basics