Question

Give an example of simple random sampling. what would be the strenghts and weaknesses of simple random sampling in terms of external validity and sampling error?

Answer 1

A simple random sample (SRS) is the simplest form of probability sample. S.R.S. is that “each and every unit of the population has equal and independent probabilities of being included in the sample”. The sample units are selected one by one from the population

Strengths and weakness of S.R.S:

1.   Since the sample units are selected at random giving each unit an equal chance of selected, the elements of subjectivity or personal biases completely eliminated. As such a simple random sample is more representative of the population as compound to the judgment or purposive sampling.
2.   S.R.S is very simple and effective method of drawing samples provided i) Population is not very large ii) The sample size is not very small iii) the population under consideration is not heterogeneous.
3.   All the test of significance is based on the concept of simple random sampling.
4.   This method is economical as it save time, money and labor.
5.   One of the major dis-advantages of S.R.S. is that all members of the population must be known and be serially numbered.
6.   A S.R.S. may result in the selection of the sampling units which are widely spread geographically and in such a case the cost of collecting the data may be much in term of time and money.
7.   For given precision S.R.S usually requires larger sample size as compared to St.R.S.
8.   This requires a complete list of the population but such up-to-date lists are not available in many inquiries.
9.   If the size of the sample is small, then it will not be a representative of the population.