Most of the educational phenomena consist of a large number of units. It would be impracticable, if not possible, to test, interview or observe each unit of the population under controlled conditions in order to arrive at principles having universal validity. Some populations are so large that their study would be expensive in terms of time, money, effort and manpower. Sampling is the process by which a relatively small number of individuals or measures of individuals, objects or events is selected and analysed in order to find out something about the entire population from which it was selected. It is often desirable in order to reduce expenditure, save time and energy, permit measurement of greater scope or produce greater precision ...

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