A select number of people who are known to be related to the topic are part of the study which means that there are lesser chances of having people who will distort the data
Good method for pretesting instruments like questionnaires.Some disadvantages are:
It can be subject to experimenter’s bias and stereotypes that may distort the results.
The group selected may not represent all the population
It might not be possible to accurately identify the sample using this method in case the population is very large.
Judgement sampling involves the choice of subjects who are most advantageously placed or in the best position to provide the information required. For instance, if a researcher wants to find out what it takes for women managers to make it to the top, the only people who can give first hand information re the women? Who have risen to the positions of presidents, vice presidents and important top-level executives in work organizations?
They could reasonably be expected to have expert knowledge by virtue of having gone through the experience and processes themselves and might perhaps be able to provide good data or information to the researcher. Thus the judgement sampling design is used when a limited number or category of people have the information that is sought. In such cases any type of probability sampling across a cross-section of the entire population is purposeless and not useful.
Judgement sampling may curtail the generalizability of the finding due to the fact that we are using a sample of experts who are conveniently available to us. However it is the only viable sampling method for obtaining the type of information that is required from very specific pockets of people who are very knowledgeable are included in the sample.
