Page 104 - DMGT209_QUANTITATIVE_TECHNIQUES_II

Unit 6: Research Design

6.6.4 Extraneous Variables Notes

These are also known as blocking variables. Extraneous variables affect the results of the
experiments.

Example: Suppose a toffee manufacturing company is making an attempt to measure the
response of the buyers to two different types of packaging, at two different locations. The
manufacturer needs to keep other aspects the same, for each group of buyers. If the manufacturer
allows the extraneous variable, namely, the price to vary between two buyer groups, then he
will not be sure as to which particular packaging is preferred by the consumers.
Here the price change is an extraneous factor.

 There are two possible course of action with respect to extraneous variables.
 Extraneous variables may be physically controlled.

Example: Price in the above example.
In the second category, extraneous variables may totally elude the researcher’s control. In this
case, we say that the experiment has been confounded i.e., it is not possible to make any conclusions
with regard to that experiment. Such a variable is known as “Confounding variable”.

Example: A company introduces a product in two different cities. It would like to know
the impact of advertising on sales. Simultaneously, the competitors’ product in one of the cities
is not available during this period due to a strike in the factory. Now, the researcher cannot
conclude that sales of their product in that city have increased due to advertisement. Therefore,
this experiment is confounded. In this case, the strike is the confounding variable.

Types of Extraneous Variables

The following are the various types of extraneous variables:
 History: History refers to those events which are external to the experiment, but occur at
the same time as experiment is being conducted. This may affect the result.

Example: Let us suppose that, a manufacture makes a 20% cut in the price of a product
and monitors sales in the coming weeks. The purpose of research is to learn about the impact of
price on sales. Meanwhile, if the production of the product declines due to a shortage of raw
materials, then the sales will not increase. Therefore, we cannot conclude that the price cut did
not have any influence on sales because the history of external events have occurred during the
period and we cannot control the event. The event can only be identified.
 Maturation: Maturation is similar to history. Maturation specifically refers to the changes
occurring within the test units and not due to the effect of the experiment. Maturation
takes place due to passage of time. It refers to the effect of people growing older. Persons
who use a particular product may discontinue using that product and may switch over to
an alternate product.

Example:
1. Pepsi is consumed when people are young. Due to passage of time, the consumer
might prefer to consume Diet Pepsi or even avoid it altogether.

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