Sampling Designs

In sampling and in sample designs, the data are collected for each and every unit (person household, shop, field, factory, etc.) as the case may be of the population or universe that is the complete set of items which are of interest in any particular situation. For e.g. if the average salary of workers working in sugar industry in India is to be computed, then salary figures would be obtained from each and every worker, working in the sugar industry and by dividing the total salary that all these workers receive by the number of workers working in the sugar industry.

The Sampling is simply the process of learning about the population on the basis of a sample drawn from it, so, in the sampling technique in spite of every unit of the universe only a part of the universe is studied and the conclusions are drawn on that basis for the whole universe. A sample is a subset of population units. The Sampling technique is the only method that can be used in certain cases, there are some cases in which the census technique is inapplicable and the only practicable means is provided by the sample method. For illustration, if one is interested in testing the breaking strength of chalks manufactured in a factory under the census technique all the chalks would be broken in the process of testing. Hence, census technique is impracticable and resort must be had to the sample method. In the same way, if the producer wants to find out whether the tensile strength of a lot of steel wires meets the specified standard, he should resort to sample method as census would mean complete destruction of all the wires. Also if the population under investigation is unlimited, then sampling is the only possible solution. The sample method is frequently used to judge the accuracy of the information obtained from a census basis. For e.g., in the population census that is conducted very often (10 years in our country) the field officers employ the sample method to determine the accuracy of information technique to obtain by the enumerators on the census basis.

Some of its main topics are:

1. Census and sample method
2. Merits of sampling
3. Methods of sampling
4. Quota and convenience sampling
5. Size of sample
6. Non-sampling errors
7. Sampling errors
8. Stratified sample