SAMPLE AND SAMPLING

INTRODUCTION

The researcher is concerned with the generalizability of the data beyond the sample. For studying any problem it is impossible to study the entire population. It is therefore convenient to pick out a sample out of the universe proposed to be covered by the study. The process of sampling makes it possible to draw valid inferences or generalizations on the basis of careful observation of variables within a small proportion of the population.

CONCEPT OF UNIVERSE, SAMPLE AND SAMPLING

Universe or Population: It refers to the totality of objects or individuals regarding which inferences are to be made in a sampling study. Or It refers to the group of people, items or units under investigation and includes every individual. First, the population is selected for observation and analysis.

Sample

It is a collection consisting of a part or subset of the objects or individuals of population which is selected for the purpose, representing the population sample obtained by collecting information only about some members of a population. It is the process of selecting a sample from the population. For this population is divided into a number of parts called Sampling Units.  

NEED FOR SAMPLING

ü  Large population can be conveniently covered.

ü  Time, money and energy is saved.

ü  Helpful when units of area are homogenous.

ü  Used when percent accuracy is not acquired.

ü  Used when the data is unlimited.

ADVANTAGES OF SAMPLING

Economical :Manageable sample will reduce the cost compare to entire population.

Increased speed :The process of research like collection of data, analysis and Interpretation of data etc take less time than the population.

Greater Scope :Handling data becomes easier and manageable in case of a sample. Moreover comprehensive scope and flexibility exists in the case of a sample.

Accuracy :Due to limited area of coverage, completeness and accuracy is possible. The processing of data is done accurately producing authentic results.

Rapport :Better rapport is established with the respondents, which helps in validity and reliability of the results.

DISADVANTAGES OF SAMPLING

Biasedness : Chances of biased selection leading to erroneous conclusions may prevail. Bias in the sample may be due to faulty method of selection of individuals or the nature of phenomenon itself.

Selection of true representative sample :It the problem under study is of a complex nature, it becomes difficult to select a true representative sample, otherwise results will not be accurate & will be usable.

Need for specialized knowledge : The researcher needs knowledge, training and experience in sampling technique, statistical analysis and calculation of probable error. Lack of those may lead to serious mistakes.

Changeability of units :If the units of population are not homogeneous, the sampling technique will be unscientific. At times, all the individuals may not be accessible or may be uncooperative. In such a case, they have o be replaced. This introduces a change in the subjects to be studied.

Impossibility of sampling :Sometimes population is too small or too heterogeneous to select a representative sample. In such cases ‘census study’ is the alternative (Information about each member of the population) Sampling error also comes because of expectation of high standard of accuracy.

CHARACTERISTICS OF A GOOD SAMPLE

A good sample should possess the following characteristics

      A true representative of the population

      Free from error due to bias

      Adequate in size for being reliable

      Units of sample should be independent and relevant

      Units of sample should be complete precise and up to date

      Free from random sampling error

      Avoiding substituting the original sample for convenience.