Population And Sample

Population and Sample

Population The totality of statistical information on a particular character, from all members covered by an investigation, is called population or universe. For Example:- population of registered management colleges in West Bengal i.e. the total number of management colleges in West Bengal.

Sample The sample is a selected part of the population and is used to throw light on the population characteristics. For example:1) In order to know the economic condition the inhabitants of Calcutta city, if the monthly income figures of each and every Calcuttan could be obtained, the whole collection of figures of income would constitute the “population of income".

This however, is impracticable to interview all the inhabitants of Calcutta , so a part of the whole population i.e. a few thousand inhabitants would ordinarily be interviewed and their income figures obtained. These few thousand figures of income would comprise a “sample of income”, based on which the average income is estimated which will reveal the characteristics of the whole population. 2) Sampling method is used in Market Research for assessing the possible market potential before launching a new product. In this case it is not feasible to interview all the consumers of the market because of the time and money constraint. So we have to select few consumers as a representative of the whole market and conduct the survey on the basis of their interview.

3) Auditors use test check and test audit to only a small fraction of all entries in the books of accounts in order to verify the accuracy of all the entries, whether either full verification is not possible or considered unnecessary.

Collection of statistical data There are two ways of collection of statistical data:1) Complete enumeration survey or census method. 2) Sample survey method.

Complete enumeration or census survey method. Under Complete enumeration survey method., data are collected from each and every member of population. For Example: Census of population in India is an classic example of complete enumeration.  In order to know the consumers reactions to a particular product, we may interview each and every person who uses that product and that will be regarded as complete enumeration survey method.

Advantages and disadvantages of complete enumeration:a) Information can be obtained for each and every unit:If the information is required for each and every unit of the population, a complete enumeration survey is necessary. For example: Preparation of voters’ list for election purpose where the information of each individual of the population is required to capture.  Income tax assessment- where income of each individual is assessed and taxed.

b) Great Accuracy:The results of the complete enumeration survey are expected to be more accurate than the sample survey method because the information is obtained for each and every unit. But it may be noted that a complete enumeration survey need not necessarily provide accurate information. The errors of complete enumeration survey arises mainly from,  Difficulties encountered in organising such a large scale survey.  Incomplete coverage of the whole population.  Tabulation error due to difficulties encountered in handling such a large scale data.  Difficulties in getting adequate trained personals in order to conduct the survey. and these errors can not be calculated. Moreover the effort, money and time required for carrying out complete enumeration will generally be extremely large.

Sample survey method. In the sample survey method, instead of studying every unit of the population, only a part of the population i.e. sample is studied and conclusions are drawn on the basis of this sample for the entire population.

Advantages of sample survey over the complete enumeration method. 1) Sample survey takes less time,labour and money than is necessary in complete enumeration, because only a part of the whole population is investigate. 2) Sample survey yields more accurate result than complete enumeration, because of the deployment of specially trained investigators and the possibility of better control and supervision over them. But complete enumeration requires a large number of investigators, all of whom cannot be expected to have proper training.

3) An extra advantage of sample survey method is that here the magnitude of the error is known and can be theoretically calculated which is not possible in case of complete enumeration. 4) In come cases, complete enumeration is not feasible and sample survey method is the only way. For example: In order to test average life of a bulb, we can not test all the bulbs because it will be destructive , so here we have to select few bulbs in order to conduct the test.  A rice merchant can not afford to examine every single grain of rice before purchase. He has to depend on sample, based on which he forms an idea about the quality of rice. Because of these advantages mentioned above the sample survey is more popular than complete enumeration.