Mention the four main merits and …

Merits:

1. Economical: 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.

3. Reliable: If sample is taken judiciously, the results are very reliable and accurate.
 

Demerits:

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.