A sample from a population is drawn and tests are conducted to make generalizations for the population as a whole. Information about the sample is considered for the purpose of studies due to time constraints in studying the entire population. Before collecting the sample, the entire population must be clearly defined. In Statistics, ‘N’ is used to denote the entire population and ‘n’ denotes the sample under consideration.
For example, to study an infant related disease, the statistical population considered would be all the infants in India or any other country where such a study is undertaken. The sample in this case could be a certain number like 5000 infants from different states. If the test identifies 2% of the sample infants surveyed suffering from the disease, it can be extended to the entire population of infants as well i.e. 2% of the entire population of infants maybe suffering from the disease.