Page 161 - DMGT209_QUANTITATIVE_TECHNIQUES_II

Quantitative Techniques-II

Notes Non-probability Sample

In this case, the likelihood of choosing a particular universe element is unknown. The sample
chosen in this method is based on aspects like convenience, quota etc.

Example: Quota sampling, Judgment sampling.

Task Identify the appropriate target population and sampling frame for various situations
listed below:
1. The regional marketing manager of a beverage company wants to test market three
new flavours to gauge their acceptance.
2. A manufacturer wants to assess whether adequate inventories of spare parts are
being maintained by the distributors to prevent shortages and loss of business.
3. A wholesaler dealing with audio/video equipments wants to evaluate the reaction
of dealers towards a new promotion policy announced.

4. A TV channel wants to determine the viewing habits of housewives and their
programme preferences.
5. A departmental chain such as Food World wants to determine the shopping behaviour
of customers who use the credit cards.

8.5 Errors in Sampling

8.5.1 Sampling Error

The only way to guarantee the minimization of sampling error is to choose the appropriate
sample size. As the sample keeps on increasing, the sampling error decreases. Sampling error is
the gap between the sample mean and population mean.

Example: If a study is done amongst Maruti car-owners in a city to find the average
monthly expenditure on the maintenance of car, it can be done by including all Maruti car-
owners. It can also be done by choosing a sample without covering the entire population. There
will be a difference between the two methods with regard to monthly expenditure.

8.5.2 Non-sampling Error

One way of distinguishing between the sampling and the non-sampling error is that, while
sampling error relates to random variations which can be found out in the form of standard
error, non-sampling error occurs in some systematic way which is difficult to estimate.
8.5.3 Sampling Frame Error

A sampling frame is a specific list of population units, from which the sample for a study being
chosen.

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