When conducting research, it is almost impossible to study the entire population. Hence, researchers use samples as a way to gather data. A sample is a subset of the population being studied. It represents the larger population and is used to draw inferences about that population. Researchers use different sampling techniques to select the participants for their sample. Various sampling techniques in research methodology are:-
- Probability Sampling- Here, every individual in the population is known and each has a certain probability of being selected. A random process decides the sample. Different probability sampling techniques are:-
a) Simple Random Sampling- It is the most basic sampling method. To collect a simple random sample, each unit of the target population is assigned a number. A set of random numbers is then generated to select units having those numbers.
b) Systematic sampling- Here, the elements of the population are put into a list and then every kth element in the list is chosen for inclusion in the sample.
c) Cluster sampling- It is used when it is impossible or impractical to compile an list of the elements that make up the target population, however, the population elements are already grouped into sub populations whose lists already exist or can be created.
d) Stratified Sampling- It is a sampling technique in which the entire target population is divided into different subgroups, or strata, and then randomly the final subjects are selected proportionally from the different strata.
2. Non-probability Sampling- It is used when the population is not entirely known, thus individual probabilities cannot be known. Common sense or ease is used to choose the sample with an effort to avoid bias. Various non-probability sampling techniques are:-
a) Convenience Sampling- Here, a sample is selected from that part of the population which is readily available and convenient, although the sample is not representative of the entire population. It is generally used for pilot testing.
b)Quota Sampling- A quota sample is one in which units are selected into a sample on the basis of some pre-specified characteristics so that the total sample has the same distribution of characteristics as it exists in the population being studied.
c) Judgement Sampling- This is also a non-random sampling method where the investigator selects the sample arbitrarily which he considers important for the research and believes it as a representative of the population.
d)Snowball Sampling- This is a sociometric sampling technique generally used to study a small group. All the persons in a group identify their friends who in turn know their friends and colleagues, until the informal relationships converge into some type of a definite social pattern. It is just like the snow ball goes on increasing its size when rolling in an ice-field. This method is suitable for diffusion of innovation, network analysis, decision making.