Page 159 - DMGT209_QUANTITATIVE_TECHNIQUES_II

Quantitative Techniques-II

Notes Sequential Sampling

This is a method in which the sample is formed on the basis of a series of successive decisions.
They aim at answering the research question on the basis of accumulated evidence. Sometimes,
a researcher may want to take a modest sample and look at the results. Thereafter, s(he) will
decide if more information is required for which larger samples are considered. If the evidence
is not conclusive after a small sample, more samples are required. If the position is still
inconclusive, still larger samples are taken. At each stage, a decision is made about whether
more information should be collected or the evidence is now sufficient to permit a conclusion.

Example: Assume that a product needs to be evaluated.

A small probability sample is taken from among the current user. Suppose it is found that
average annual usage is between 200 to 300 units. It is known that the product is economically
viable only if the average consumption is 400 units. This information is sufficient to take a
decision to drop the product. On the other hand, if the initial sample shows a consumption level
of 450 to 600 units, additional samples are needed for further study.

Quota Sampling

Quota sampling is quite frequently used in marketing research. It involves the fixation of
certain quotas, which are to be fulfilled by the interviewers.
Suppose, 2,00,000 students are appearing for a competitive examination. We need to select 1% of
them based on quota sampling. The classification of quota may be as follows:

Example: Classification of Samples
Category Quota
General merit 1,000
Sport 600
NRI 100
SC/ST 300
TOTAL 2,000
Quota sampling involves the following steps:

1. The population is divided into segments on the basis of certain characteristics. Here, the
segments are termed as cells.
2. A quota of unit is selected from each cell.

Advantages

1. Quota sampling does not require prior knowledge about the cell to which each population
unit belongs. Therefore, this sampling has a distinct advantage over stratified random
sampling, where every population unit must be placed in the appropriate stratum before
the actual sample selection.

2. It is simple to administer. Sampling can be done very quickly.
3. The necessity of the researcher going to various geographical locations is avoided and
thus cost is reduced.

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