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Unit 8: Sampling and Sampling Distribution

8.3.2 Non-probability Sampling Techniques Notes

1. Deliberate sampling
2. Shopping Mall Intercept Sampling
3. Sequential sampling
4. Quota sampling

5. Snowball sampling
6. Panel samples

Deliberate or Purposive Sampling

This is also known as the judgment sampling. The investigator uses his discretion in selecting
sample observations from the universe. As a result, there is an element of bias in the selection.
From the point of view of the investigator, the sample thus chosen may be a true representative
of the universe. However, the units in the universe do not enjoy an equal chance of getting
included in the sample. Therefore, it cannot be considered a probability sampling.

Example: Test market cities are being selected, based on the judgment sampling, because
these cities are viewed as typical cities matching with certain demographical characteristics.

Shopping Mall Intercept Sampling

This is a non-probability sampling method. In this method the respondents are recruited for
individual interviews at fixed locations in shopping malls. (For example: Shopper ’s Shoppe,
Food World, Sunday to Monday). This type of study would include several malls, each serving
different socio-economic population.

Example: The researcher may wish to compare the responses of two or more TV
commercials for two or more products. Mall samples can be informative for this kind of studies.
Mall samples should not be used under following circumstances i.e., if the difference in
effectiveness of two commercials varies with the frequency of mall shopping, change in the
demographic characteristic of mall shoppers, or any other characteristic. The success of this
method depends on “How well the sample is chosen”.

Merits

1. It has a relatively small universe.
2. In most cases, it is expected to give quick results. The purpose of deliberate sampling has
become a practical method in dealing with economic or practical problems.
3. In studies, where the level of accuracy can vary from the prescribed norms, this method
can be used.
Demerits

1. Fundamentally, this is not considered a scientific approach, as it allows for bias.
2. The investigator may start with a preconceived idea and draw samples such that the units
selected will be subjected to specific judgment of the enumerator.

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