Purposive or Judgement Sampling
Under this method of sampling, the choice of selection of sample items from the universe depends exclusively on the judgement of the investigator. For example, if 10 students form a class of 60 students are to be selected for the survey of spending habits of students the 10 items may be selected by the investigator himself which he considers to be representative of the whole class.
(1) Where small number of units is in the inverse, random selection may miss the vital elements, but this method of sampling would surely include them in a simple.
(2) Where an investigator wishes to study some unknown traits of the universe and some of which are know. Thus he will stratify the universe according to known elements to select sample units form each stratum on the basis of judgement as such this method is used obtain more representative sample.
(3) This method saves time and money both as public officials are often pressed for time.
This method is unscientific since the units selected from the universe may be affected by personal bias.
The success of this method depends upon excellence in judgement, if the investigator has no good judgement, sample will not be representative. The conclusions based on sample will be wrong and erroneous.