Any statistical investigation tries to obtain information about the data. This information can be obtained in two ways, which are known as the methods of statistical investigation.
The methods are of two types – Census Method and Sample Method.
- Census Method : When the investigator collects information from all the units and elements, then it is called census method. Under this, information about each and every unit of the aggregate is collected. Population census is an example of census method. Under population census, information is obtained about every household and every person. This information is expansive. The results derived from this method are authentic and reliable. This method is costly and labour and time involved is also more.
- Sample Method : Under this, some representative units are selected from the aggregate and conclusions are derived through study of those selected units. In daily life, while purchasing things for household such as wheat, rice, etc. we do not inspect each and every piece of wheat or rice in the packet, rather we take sample of some pieces and decide to purchase wheat or rice on this basis. Time and money is saved through this method. It is important to maintain extreme caution in this method, otherwise the possibility of deriving incorrect conclusions may arise. Sample or paradigm policy is based on three principles which are known as sampling principles. The major three principles are Principle of Probability, Principle of Statistical Regularity and Principle of Inertia of Large Numbers.
