Non Probability and its Types

Non probability sample

Definition

Non-probability sampling is a sampling technique where the samples are gathered in a process that does not give all the individuals in the population equal chances of being selected.

The difference between nonprobability and probability sampling is that nonprobability sampling does not involve random selection and probability sampling does.

Types of Non Probability

Convenience sampling

Judgment sampling

Quota sampling

Convenience Sampling

Convenience sampling is a non-probability sampling technique where subjects are selected because of their convenient accessibility and proximity to the researcher.

Example

Samples those are familiar to the researcher like :

Friends, Co-workers, that is easily accessible to the researcher.

Advantages & Disadvantages

Advantages

• Saves time, money and effort.

• Easy data collection through a known group or class.

Disadvantages

• No accurate way to assess representativeness of

samples.

• Possible restrictions of generalization about the

study findings.

Judgment Sampling

Judgmental sampling is a non-probability sampling technique where the researcher selects units to be sampled based on their knowledge and professional judgment.

Example

Suppose 100 boys are to be selected from a college with 1000 boys. If nothing is known about the students in this college, then the investigator may visit the college and choose the first 100 boys he meets. Or he may select 100 boys all belonging to 3rd

Year. Or he might select 25 boys from Commerce course, 25 from Science courses, 25 boys from Arts courses and 25 from Fine arts courses.

Hence, when only the sample size is known, the investigator uses his judgment and select the sample.

Advantages & Disadvantages

Advantages

• Samples are chosen well, based on a certain criterion.

• There is assurance of quality responses.

Disadvantages

• Unfairly selection of samples may occur.

• Time-consuming process.

Quota Sampling

In this method, the sample size is determined first and then quota is fixed for various categories of population, which is followed while selecting the sample.

Example

Suppose we want to select 100 students, then we might say that the sample should be according to the quota given below :

Boys 50%, Girls 50% Then among the boys, 60% college students,

30% high school students and 10% elementary school students.

A different or the same quota may be fixed for the girls.

Advantages & Disadvantages

Advantages

• Useful when the research budget is very tight.

Disadvantages

• The result might be at risk that the sample would not

be typical of the desired sample quality.

THE ENDThanks for paying attention…