Non-probability Sampling Methods ||Estimation and Hypothesis||Bcis Notes

Non-probability Sampling Methods:

Under these non-probability sampling methods of sampling, there is no pre-assigned probability of selection of sample units to be included in the sample. Some of the methods of non-probability are given as follows:

 Types:

1. Judgment/purposive sampling:

In this method, the researcher deliberately or purposively selects the sample units based on their own knowledge or experience for the study of the population. The choice of the selection is supreme and nothing is left to chance.

 

Advantages/merits and disadvantages/demerits of the purposive sampling:

Merits:

1. If proper care is taken in selecting the sample to keep out any bias, the sample may represent the population.
2. This method is very cheap as compared to probability sampling.
3. It is more useful when some of the units are very important and must be included.

 

Demerits:

1. The knowledge of the population must be available, which in most cases is not possible.
2. This method may produce a biased sample.
3. Sample Statistics cannot be used to estimates the population parameters at a statistically defined precisions level.

 

2. Convenience sampling:

In this method, the researcher selects the sample units according to their convenience in terms of availability and accessibility of the sample units. This is one of the most unscientific methods of sampling.

 

Advantages/merits and disadvantages/demerits of convenience sampling:

Merits:

1. This method is easy to administer as compared to other methods.
2. This method is very cheap as compared to probability sampling.
3. This method does not require the frame/list.

Demerits:

1. This method may produce a biased sample.
2. Sample Statistics cannot be used to estimates the population parameters at a statistically defined precisions level.

 

3. Quota sampling:

This is a special form of stratified sampling. In this method, the population is divided into different strata. Then the number of sample units (quota) for each stratum is decided and the researcher selects the sample units from each stratum to fulfill the desired quota of each stratum according to their conveniences. This method is used mostly in opinion surveys.

 

Advantages/merits and disadvantages/demerits of the quota sampling:

Merits:

1. This method is easy to administer as compared to other methods.
2. This method is very cheap as compared to probability sampling.
3. This method does not require the frame/list.

Demerits:

1. This method may produce a biased sample.
2. Sample Statistics cannot be used to estimates the population parameters at a statistically defined precisions level.

 

4. Snowball sampling:

In this method, the researcher selects the sample units according to the referral process of the previous respondents. This method is used when it is difficult to find the sample units for the study.

 

Advantages/merits and disadvantages/demerits of the snowball sampling:

Merits:

1. This method is easy to administer as compared to other methods when there is difficulty to find the sample units.
2. This method is very cheap as compared to probability sampling.
3. This method does not require the frame/list.

 

Demerits:

1. This method may produce a biased sample.
2. Sample Statistics cannot be used to estimates the population parameters at a statistically defined precisions level.

 

5. Self-selected sampling:

In this method, the sample is not actually selected but people themselves come to participate in the sample. People have full discretion whether or not they want to include in the sample. This method is more frequently used by TV, Radio, and newspapers, etc.

 

Advantages/merits and disadvantages/demerits of the self-selected sampling:

Merits:

1. This method is very easy to administer as compared to other methods.
2. This method is very cheap as compared to probability sampling.
3. This method does not require the frame/list.

Demerits:

1. This method may produce a biased sample.
2. Sample Statistics cannot be used to estimates the population parameters at a statistically defined precisions level.

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