Sampling is the act, process, or technique of selecting a suitable sample, or a representative part of a population for the purpose of determining parameters or characteristics of the whole population.
REASONS FOR SAMPLING
There are six main reasons for sampling instead of doing a census. These are; * Economy * Timeliness * The large size of many populations * Inaccessibility of some of the population * Destructiveness of the observation * Accuracy or Reliability
Economy
The economic advantage of using a sample in research obviously, taking a sample requires fewer resources than a census. Unit cost of collecting data in the case of census is significantly less then in the case of sampling for example: In case of census is taka 200, while in the case of sampling is taka 1,000 but due to the larger number of items the total cost involve in the case of census of census is significantly higher then in the case of sampling.
Timeliness
Unit time involve in the case of sampling then in the case census but due to the larger size of population total time involve in the case of census in significantly higher then in the case of census.
Large size of many populations
In some cases the size of the population is extremely large. All of them are not treaseable due in traveling, disease, death, mental abnormality, prisoners etc. In that situation the only way to conduct the research is collecting data through a sample survey.
Inaccessibility of some of the populations
In some cases the entire population may not be accessible. At that case sampling is necessary. Suppose in some cases the entire population is inaccessible because of aircraft crash.
Destructiveness of the observations
Due to destructive nature of many of the population, the resources is completed to collect information only on a part of the population.
For example: Blood test for a patient.
Life hours of a tube light.
Accuracy or reliability
By using a scientific sampling