All items in any field of inquiry constitute a ‘ Universe ’ or ‘ Population.’ A complete enumeration of all items in the population is known as a census inquiry. It can be presumed that in such an enquiry, when all items are covered, no element of chance is left and highest accuracy is obtained. But in practice this may not be true. Even the slightest element of bias in such an inquiry will get larger and larger as the number of observation increases. Moreover, there is no way of checking the element of bias or its extent except through a resurvey or use of sample checks. Besides, this type of inquiry involves a great deal of time, money and energy. Therefore, when the field of inquiry is large, this method becomes difficult to adopt because of the resources involved. At times, this method is practically beyond the reach of ordinary researchers. Perhaps, government is the only institution which can get the complete enumeration carried out. Even the government adopts this in a very rare cases such as population census conducted once in a decade. Further, many a time it is not possible to examine every item in the population, and sometimes it is possible to obtain sufficiently accurate results by studying only a part of total population. In such cases there is no utility of census surveys.
A census refers to a count or a study of all of the elements in the ‘ Population’. As is quite obvious it is generally more economical in time, efforts and money to get the desired information for only some of the elements ( sample ) than for all of them, i.e., the population. When we select some of the elements ( sample ) with the intention of finding out something about the population from which they are taken, we refer to that sub - group of elements of a ‘ Sample ’. Our expectation, in studying the sample, is of course, that what we find out from the sample, will be true of the ‘ population ’ as a whole. Actually this may not be the case, since after all; a sample is only a part of the whole population.
How far would the information of findings we get from the sample, approximate the finding we would get if the totality, i.e., the given population, were studied and whether or not out finding based on the study of a sample is likely to differ from the finding. What we would get if the given population as a whole was studied, by more than a specific margin of value, would depend greatly on the way sample is selected.
Of course, we can never have the full assurance that our sample returns reflect the state of the population with respect to the characteristics we are studying, unless we have simultaneously conducted a complete comparable study of the population.
However, it needs to be emphasized that when the universe is a small one, it is no use resorting to a sample survey. When field studies are undertaken in practical life, considerations of time and cost almost invariable lead to a selection of respondents i.e. selection of only a few items. The selected respondents constitute what is technically called a ‘ Sample ’ and the selection process is called ‘ Sampling Technique. ’ The survey so conducted is known as ‘ Sample Survey. ’ There are various methods of Sampling.
1.Deliberate sampling or purposive sampling.
3.Stratified random sampling.
5.Multi stage sampling.
There are various main features of sampling technique :
The sampling technique has following good features and these bring into relief its value and significance. 1.Economy : the sampling technique is much less expensive, much less time consuming than the census technique. 2.Reliability : if the choice of sample units is made with due care and the matter under survey is not heterogeneous, the conclusion of the sample survey can have almost the same reliability as those of census survey. 3.Detailed study : Since...