Page 160 - DMGT209_QUANTITATIVE_TECHNIQUES_II

Unit 8: Sampling and Sampling Distribution

Limitations Notes

1. It may not be possible to get a “representative” sample within the quota as the selection
depends entirely on the mood and convenience of the interviewer.
2. Since too much liberty is being allowed to the interviewer, the quality of work suffers if
they are not competent.

Snowball Sampling

This is a non-probability sampling. In this method, the initial groups of respondents are selected
randomly. Subsequent respondents are being selected based on the opinion or referrals provided
by the initial respondents. Further referrals will lead to more referrals, thus leading to a snowball
sampling. The referrals will have demographic and psychographic characteristics that are
relatively similar to the person referring them.

Example: College students bring in more students on the consumption of Pepsi. The
major advantage of snowball sampling is that it monitors the desired characteristics in the
population.
Panel Samples

Panel samples are frequently used in marketing research. To give an example, suppose that one
is interested in knowing the change in the consumption pattern of households. Samples of
households are drawn. These households are contacted to gather information on the pattern of
consumption. Subsequently, say after a period of six months, the same households are approached
once again and the necessary information on their consumption is collected.
Self Assessment

Fill in the blanks:
7. ..................... is also called as the random sampling with replacement.
8. ..................... is also called random sampling without replacement.
9. Stratified sampling can be carried out with ..................... proportion across the strata
proportionate stratified sample.
10. In cluster sampling, ..................... the units in the selected cluster are studied.

8.4 Distinction between Probability Sample and

Non-probability Sample

Probability Sample

1. Here, each member of a universe has a known chance of being selected and included in the
sample.

2. Any personal bias is avoided. The researcher cannot exercise his discretion in the selection
of sample items.

Example: Random Sample, cluster sample.

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