Sampling Methods/Sampling Designs

Sample designs are different methods used for the conduct of sample survey. Quota sampling, judgment sampling etc. are the non-probability sample designs while random sampling,area sampling, etc. are the probability sample designs. In brief, the sample designs are divided into the following two categories:

(a) Probability Sampling Methods

(b) Non-Probability Sampling Method

(a) Probability/Random Sampling Methods

In the probability sampling methods, the sample units are selected at random. This means the selection is haphazard/arbitrary. Every member in the universe has equal chance of being selected as the representative. The fact that any item can be selected is known. The selection of sampling item is impartial and independent of the person making the study. There is no scope for any biased selection of sample units.

Probability sampling methods include random sampling, stratified, cluster, sampling, etc. Such methods are used extensively in marketing research. These methods provide unbiased information. The probability sampling methods are objectively designed. However, these methods are time consuming and also costly for use. Greater statistical competence and time are required to plan and use probability sampling methods.

(b) Non-probability Sampling Methods

Here, sample units are selected in a non-random manner. The selection may be purposive. It may be based on the convenience or the judgment of the researcher. The selection is deliberating not random. Every item is not given a definite chance of being included in the sample. The non-probability sampling ‘ methods include convenience sampling, judgment sampling, and quota sampling. In these methods, the sample is selected in a subjective manner and the decision regarding sample is taken by the researcher himself. The sample selected may not be representative of the universe to be studied. The selection of sample may be influenced by the subjective consideration of the person connected with research work (researcher).

Non-probability sampling methods are also used in marketing research along with probability methods. Such methods are sometimes preferred because they cost less per observation, require less time and need relatively little statistical sophistication in planning the sample design and in the selection the respondents. Probability sampling methods are more scientific and capable of yielding more representative samples than non-probability sampling methods. However, there is no sampling method (probability or non-profitability) that can be considered to be best in all situations. Any suitable method may be selected and used properly for promising results.