This method of data collection is also known as complete enumeration technique or 100% enumeration technique. Under this technique each and every item or unit constituting the universe is selected for data collection. In the Indian census, which is conducted once in every ten years, this technique is invariably followed.
Examples: Suppose we have to study
"Sale and Profit of Sugar industry in U.P." Suppose there are 2000 sugar mills in U.P. If the investigator has to collect data of all these mills, investigation will be called census method. Suppose we have to study,
"Average income of all households in Chandigarh" Suppose, there are 25,000 households in Chandigarh. If we collect and analyze data for all these households, investigation will be based on census method.
(i) Accuracy in the Result:
Under this technique of data collection, the result of the enquiry is likely to be exact and accurate. This is because the information's are collected from each and every unit of the universe without ignoring any one.
(ii) Extensive Study:
Under this technique of data collection an extensive and detailed study of the unit is made possible. For example, in the population census a lot of information relating to the population viz age, sex, marital status, religion, nationality, education, occupation, employment, income, wealth etc. are all collected in addition to the number of individuals constituting a unit.
This technique of data collection is highly expensive. It requires lot of manpower and administrative personnel as well. Therefore, this type of technique cannot be afforded by small organizations.
(ii)May not Meet with Urgency:
Since the technique takes a lot of time collecting the data from each and every item, it may not be possible to meet with an urgent situation by answering to a problem under study promptly. Moreover, in course of the long period, conditions of the phenomenon might have radically changed so that the result obtained from the enquiry may not truly represent the situation. For example in the measurement of price level changes, the price index number arrived at after long time does not speak of the true picture of the price level in the economy.
This technique of data collection cannot be applied where the universe is infinite or hypothetical. It also, cannot be applied, where, in course of stud; the item itself is destroyable.
However, this technique of data collection is advisable in the following cases
1. Where it is necessary to make complete enumeration in detail of the constituting a universe like that of census of population.
2. Where it necessary to have the exact and accurate results and a slight in the result is likely to cause loss of life or serious causalities to people serious damages to the machineries and equipments. For example, in the of a factory manufacturing some medicines census technique of data collection is very much advisable.
3. Where the size of the universe is considerably small.
4. Where the quality of the incoming lot or the units is very poor or unknown.