TYPES OF SAMPLING – Contd..

Among all the previously discussed sampling techniques, the most widely and effectively used techniques include Deliberate Sampling and Simple Random Sampling.

1. Deliberate Sampling

It is a kind of non-probability sampling that involves the selection of components based on factors excluding random chance. This type of sampling involves the chance of unequal selection of members of the population. Hence, it is not reliable to assume that the sample represents the target population completely, as it might be possible that the researcher intentionally chose the individuals to participate in the study.

Deliberate sampling method is useful for case studies, pilot studies, qualitative research, and hypothesis development. This sampling technique is generally applied in studies, which are not interested in the parameters of the total population. For example, if you are interested to find out the particular reaction of some students on the devaluation of the rupee, then instead of asking the opinions of all students in various college/universities of Delhi, you may deliberately ask only the student leaders of a particular college/university.

Deliberate sampling method is more preferred as it is easy, quick, and cost-effective. However, the findings of the sample survey cannot be universal to the entire population as the sample is not representative. Since there is no set criterion for sample selection, there is a scope for research being persuaded by the preference of the researcher.

2.  Simple Random Sampling

It is a kind of probability sampling, which provides each member of the population with a calculable and non-zero probability of selection in the sample. Since every member is given an equal chance of being selected, this type of sampling is thus considered as a reliable way of selecting a sample from a given population.

The benefits of simple random sampling can be obtained when the target population size is small, homogeneous, and not much information is available regarding the population. For example, if we have a list of 70 heads of households, each having a unique number. We want to select 30 random households from this list. By the help of a random number table, we select consecutive 2-digit numbers from the table. If a random number matches a household’s number, then that household will be added to the list of selected households. Similarly, if a random number does not match a household’s number (e.g., if it is greater than 70), then it is not added to the list of selected households. Each random number that is used is crossed out to avoid repetition. In this way, we continue to select households until we have 30.

Simple random sampling is quite advantageous as it is free of classification error and needs minimum innovative knowledge of the population. However, this sampling method is usually not preferred as it becomes crucial to list every item in the population prior to the sampling and requires a huge sampling frame, which can result in massive sampling calculations and extreme costs.

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Types of Sampling

Sampling can be basically categorized into probability and non-probability sampling. In probability sampling, each and every element of the population has a probability of being selected in the sample, i.e., the probability can be accurately measured. Whereas, in non-probability sampling, not all elements have a chance of being selected in the sample, i.e., their probability cannot be accurately measured.

The commonly used sampling methods are given below:

»  Deliberate sampling: It is a non-probability sample design in which the researcher purposively or deliberately selects certain units of the universe to form a sample that would represent the universe. In other words, it is a sampling with a purpose. It is also known as purposive sampling.

 

»  Simple random sampling: It is a probability sample design where each and every element has an equal probability of being selected in the sample. It is also known as chance sampling.

 

»  Systematic sampling: In this method, elements from a large population are selected at periodic intervals according to a random starting point, i.e., every nth element is selected for the sample, where n can be any random position of an element.

 

»  Stratified sampling: In this method, the researcher divides the entire population into different subgroups or strata, and then randomly selects elements proportionally from the strata to include in the sample.

 

»  Quota sampling: It is a non-probability sample in which the researcher selects random units for a sample according to certain given criteria or quota. In other words, elements are selected according to pre-specified criteria in such a way that the sample represents the same characteristics of the population under study.

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