The methods, using which, we can get the samples; below are given its merits and demerits on the whole.
It is economical, because we have not to collect all data. Instead of getting data from 5000 farmers, we get it from 50-100 only.
2. Less Time Consuming:
As no of units is only a fraction of the total universe, time consumed is also a fraction of total time. Number of units is considerably small, hence the time.
If sample is taken judiciously, the results are very reliable and accurate.
4. Organisational Convenience:
As samples are taken and the number of units is smaller, the better (Trained) enumerators can be employed by the organisation.
5. More Scientific:
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.”
It is based on certain laws such as:
(a) Law of Statistical Regularity
(b) Law of Inertia of Large numbers
(c) Law of Persistence
(d) Law of Validity.
6. Detailed Enquiry:
A detailed study can be undertaken in case of the units included in the sample. Size of sample can be taken according to time and money available with the investigator.
7. Indispensable Method:
If universe is bigger, there remains no option but to proceed for this method. It is specially used for infinite, hypothetical and perishable universes.
1. Absence of Being Representative:
Methods, such as purposive sampling may not provide a sample, that is representative.
2. Wrong Conclusion:
If the sample is not representative, the results will not be correct. These will lead to the wrong conclusions.
3. Small Universe:
Sometimes universe is so small that proper samples cannot be taken not of it. Number of units are so less.
4. Specialised Knowledge:
It is a scientific method. Therefore, to get a good and representative sample, one should have special knowledge to get good sample and to perform proper analysis so that reliable result may be achieved.
5. Inherent defects:
The results which are achieved though the analysis of sampling data may not be accurate as this method have inherent defects. There is not even a single method of sampling which has no demerit.
6. Sampling Error:
This method of sampling has many errors.
7. Personal Bias:
As in many cases the investigator, chooses samples, such as convenience method, chances of personal bias creep in.