It is often required to collect information from the data. There two methods for collecting the required information.
- Complete information
In this method the required information are collected from each and every individual of the population. This method is used when it is difficult to draw some conclusion (inference) about the population on the basis of sample information. This method is costly and time consuming. This method of getting data also called Complete Enumeration or Population Census.
Sampling is the most commonly and wisely used method of collecting the information. In this method instead of studying the whole population only a small part of population is selected and studied and result is applied to the whole population. For example, a cotton dealer picked up a small quantity of cotton from different bale in order to know the quality of the cotton.
Purpose or objective of sampling
Two basic purposes of sampling are
- To obtain the maximum information about the population without examining each and every unit of the population.
- To find the reliability of the estimates derived from the sample, which can be done by computing standard error of the statistic.
Advantages of sampling over complete enumeration
- It is much cheaper method to collect the required information from sample as compare to complete enumeration as lesser units are studied in sample rather than population.
- From sample, the data can be collected more quickly and save time a lot.
- Planning for sample survey can be done more carefully and easily as compare to complete enumeration.
- Sampling is the only available method of collecting the required information when the population object/ subject or individual in population are of destructive nature.
- Sampling is the only available method of collecting the required information when the population is infinite or large enough.
- The most important advantage of sampling is that it provides reliability of the estimates.
- Sampling is extensively used to obtain some of the census information.
For further reading visit: Sampling Theory and Reasons to Sample