Let us make an in-depth study of the two methods for collecting statistical data.
1. Census Method:
The data which are collected by the investigator himself is called primary data. Census data can be thought of as primary data.
When the data collector or investigator collects data or information about each and every item in the population and other related areas, it is known as census method. As this method deals with the investigation of the entire population, it is also called complete enumeration method.
If a survey covers 100 p.c. population, it is called a census method. In other words, here each and every item or unit constituting the ‘entire population’ or ‘the universe’ is selected for statistical enquiry. If a statistical enquiry is conducted to study the nature and pattern of urbanisation, then the universe consists only of the urban population of India. This method is called complete enumeration method because information from each and every unit belonging to India’s urban population is collected.
Merits of Census Method:
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First, for an extensive study (however expensive it may be) this method is considered to be an ideal one. For example, in the population census, we obtain quite a large number of key information, such as birth rate, death rate, infant mortality rate, literacy rate, ratio of urban-rural population, trend on urbanisation and so on.
Secondly, accuracy in the results is obtained. The data collected are more accurate and reliable under this census method since information are gathered from various angles. However, reliability in data and their accuracy in results are surely obtained provided enumerators do their work honestly and sincerely.
Demerits of Census Method:
First, being extensive in nature, the complete enumeration method is much expensive since a considerable amount of money, time, and labour are demanded and involved.
Secondly, this method is often not feasible or practicable because the concept of the ‘universe’ is hypothetical. Since “universe” is the basis of data collection, its applicability becomes very much limited. This method cannot be met with urgency.
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This means that if an urgent statistical information for the entire population for policy purposes is needed, this method will surely be less helpful. In other words, it is too cumbersome and inefficient to obtain a complete picture of the target population.
Thirdly, in the census method, often large number of non-sampling errors creeps in. This means that results obtained may not be uniform.
2. Sample Survey Method:
Instead of the census method, data analysts often consider a portion or a sample of the population. If a sample population—instead of full survey of a population—is investigated then we have sample survey method or portion enumeration method.
A sample is anything less than a full survey of a population. For example, liquor consumption among college and university students is to be investigated. For this purpose, a small number of students following a particular prescribed technique will be picked up (sample drawn) and their habits for consumption of liquor will be investigated. The primary objective of such sample enquiry is to estimate some characteristics of the population from which the sample is selected.
Merits of Survey Method:
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Sample survey method has many advantages over census method. That is why this method is more popular than the latter method. In the words of A. C. Rosander, “If carefully designed, the sample is not only considerably cheaper but may give results which are just accurate and sometimes more accurate than those of a census technique.”
This method is preferable for the following reasons:
First, since only a part of the population is investigated under this method, it takes less time, less money and less labour. There is saving in time also since sampling enquiry requires less fieldwork, tabulation and data processing than a full survey method. Sample survey method can be conducted when the investigators face the problem of budget constraint. It is cheaper to collect information from a sample group.
However, for conducting the entire enquiry, small group of investigators or specialist investigators are paid huge amount and employed but the output is much more. That is why it is also said that this method results in reduced unit cost of enquiry.
Secondly, conclusions and results obtained from this method are more accurate and reliable as fewer or chosen sample units are surveyed. Trained personnel are usually employed to collect data and investigate the problem. Above all, these people use sophisticated and latest designed techniques so that results become more accurate and reliable. Further, it is true that sampling errors cannot be avoided, but such errors are easier to estimate and control.
Thirdly, the small sample data provide a good benchmark for the entire population.
Finally, from the administrative point of view, the sample method is considered as an ideal one as the organisation as well as administration considers the process practically more convenient. Administrative network does not usually require to be considerably elaborate or extensive.