Principles and Techniques of Veterinary and AH Extension

NON-PROBABILITY/ NON-RANDOM SAMPLING

• It does not adopt the theory of probability and it does not also give a representative sample of the population.

Convenience Sampling / Accidental Sampling

• This is hit or miss procedure of study. The investigator selects certain units from the population as per his convenience. No planned effort is made to collect information. This type of sampling is commonly used more often in Journalism. The Journalists interviews those people whom he happens to meet.
• Ex: Asking the known farmers or familiar persons about their reactions on budget or extent of damage to crops because of floods.

Deliberate / Purposive / Judgement Sampling

• This method means deliberate selection of sample units that conform of some pre-determined criteria. This involves selection of cases, which are considered as the most appropriate ones for the given study. It is based on the judgment of the researcher or expert.
• Ex: To study the utilization of credit facilities by small farmers, the investigator needs to identify only small farmers and include them as a sample of the study.

Quota sampling

• When the population is known to consist of various categories by sex, age, religion etc. each investigator may be given assignment of quota, groups specified by the predetermined traits in specific proportions. One can select accessible persons belonging to these quota groups.

Snowball Sampling

• This is the colourful name for a technique of building up a list of sample population. In this method sample units are selected by using an initial set ot its members as informants.
• Ex: If a researcher wants to study the problems faced by dairy farmers, he may identify an initial group of farmers through some source like veterinary hospital, milk co-operative societies etc. Later, he can ask one of them to indicate names of other dairy farmers known to them.

Extensive Sampling

• This method is virtually same as census except that the irrelevant items are left out and every other item is examined.
• For example, to study consumer behaviour of Pondicherrians, foreigners living in Pondicherry are to be excluded.