Brief notes on Sampling Method of data collection
Under this technique some representative units or informants are selected from the universe. Brief notes on Sampling Method of data collectionThese selected units are called samples. Based upon the data collected fro these samples conclusions are drawn upon the whole universe.
It is to be noted that if the size of the sample is considerably large and the samples have been properly selected various results obtained from the study of the sample units, also, hold good for the entire universe.
Suppose we have to study the average monthly expenditure of say, 5000 students reading in Orissa university, we may select few students say 500 only from them as samples and collect the information on their monthly expenditure from them.
The average of monthly expenditure of these 500 students would be the average monthly expenditure of all the 5000 students reading in the university provided these 500 students were selected properly as samples.
"Sales and Profits of cycle Industry in Orissa." Suppose there are 1000 cycle units in Orissa. Now, if we collect and analyze the data for 60 units, method of investigate will be termed as Sample Method.
In the similar manner, the results relating to the various measures of the sample called "Statistic" viz. average, dispersion, skewness, coefficient of correlation etc. of a samples, would be the results of the corresponding measures of the population called 'parameters' viz. average, dispersion, skewness, coefficient of correlation etc. of the population.
The various statistical information's relating to a population that is sustained under this technique is known as inductive statistics or statistical inferences. This statistical information's are drawn about the totality of cases or items termed as population on the basis of examining a part of the population termed as sample drawn from the population in a scientific manner.
In the words of A.C. Rosander, "The sample has many advantages over a census or complete enumeration. If carefully designed, the sample is not only considerably cheaper but may give results which are just accurate and sometimes more accurate than those of a census technique. Hence, a carefully designed sample may actually be better than a poorly planned and executed census."
According to Prof. R.A. Fisher, the sample technique has four important advantages over census technique of data collection. They are "Speed, Economy, Adaptability and Scientific approach."
Thus, the chief advantages of the sample technique may be enumerated as under:
(i) Speed or Saving in Time:
Under this technique a statistical investigation is carried out speedily and consequently a lot of time and energy is saved not only in the collection of the data but also in the processing, editing and analyzing these data. This is because in sample enquiry, only a part of the universe is contacted and studied instead of each and every unit of the universe. As such this technique is more preferred to census technique where the results of the investigation are needed most urgently and quickly.
(ii) Economy or Saving in Time:
Under this technique a lot of expenses are saved both in terms of money and energy not only in the collection of data but also in the ministration, transport and training etc. This is because in sample technique only an action of the population is studied and examined to arrive at the desired conclusion, thus, economy is maintained in all the phases of the enquiry conducted under this technique.
The sample technique of data collection, unlike census technique is very much adaptable to the changes in the circumstances of the universe. This means that the size of the sample can be increased or decreased according to the size of the universe, availability of resources and the degree of accuracy desired.
Similarly, the nature of the sample technique, also, can be changed according to the nature, object and scope of the enquiry. Thus the sample technique of data collection is very much flexible and adaptable to the changes in conditions of the enquiry.
(iv) Scientific Approach:
The sample technique of data collection is very much Scientific in its approach. Particularly, the techniques of random sampling are based on the Theory of Probability which is a mathematical concept.
Besides, this technique is based on certain important laws and principles viz. (i) Law of Statistical Regularity. (ii) Law of Inertia of Large Numbers, (iii) Principle of Persistence, (iv) Principle of Optimization, (v) Principle of validity, (vi) It is also possible to ascertain the extent of sampling error and degree of reliability of the results under this technique.
(v) Administrative Convenience:
Under this technique of data collection we find administrative convenience in as much as the number of units to be studied here is usually very limited and the number both of field and administrative staff to be maintained, therefore, is very less.
There is little botheration in the recruitment, training control and supervision of the various staff required under this method of enquiry their number will be very few.
(vi) Dependability or Reliability:
The result of enquiry derived under the sample technique is more dependable than those derived under the census technique. The because under the sample technique it is always possible to determine the extent sampling errors and the degree of reliability of the results in terms of probability.
The sample technique of data collection is found indispensable in certain types of universe viz. infinite universe, hypothetical universes and universe liable to be destroyed through testing. In case of these universes technique can never be applied.
(i) Inaccuracy in Results:
The sample technique may lead to inaccurate misleading results of the enquiry, if the selected units of the sample did not m~ properly and the personnel conducting the survey are not properly trained and from bias.
The sample technique may be expensive in terms of both mi time and energy, if the size of the sample is considerably large and the procedure ado in the technique is complicated. Moreover, it needs the services of qualified, skilled, experienced and trained personnel which entail heavy amount of expenditure.
In certain cases of statistical study, where, information needed from each and every unit of the universe and the universe comprises of the of heterogeneous nature, the sample technique of data collection is not at all suitable Moreover, if the field of enquiry is very small, this technique of data collection is suitable.
(iv) Inherent Defects in the Methods:
Each of the various methods of the sample technique suffers from certain inherent defects which can never be rooted out. Hence, the results obtained through the sample technique can never be flawless or free from all defects.