Page 43 - DMGT404 RESEARCH_METHODOLOGY

Unit 3: Research Design

1. Longitudinal Study: These are the studies in which an event or occurrence is measured Notes
again and again over a period of time. This is also known as 'Time Series Study'. Through
longitudinal study, the researcher comes to know how the market changes over time.
Longitudinal studies involve panels. Panel once constituted will have certain elements.
These elements may be individuals, stores, dealers, etc. The panel or sample remains
constant throughout the period. There may be some dropouts and additions. The sample
members in the panel are being measured repeatedly. The periodicity of the study may be
monthly or quarterly etc.

Example: For longitudinal study, assume a market research is conducted on ready to eat
food at two different points of time T1 and T2 with a gap of 4 months. Each of the above two
times, a sample of 2000 household is chosen and interviewed. The brands used most in the
household is recorded as follows.

Brands At T1 At T2
Brand X 500(25%) 600(30%)
Brand Y 700(35%) 650(32.5%)
Brand Z 400(20%) 300(15%)
Brand M 200(10%) 250(12.5%)
All others 200(10%) 250(12.5%)
200 100%

As can be seen between period T1 and T2 Brand X and Brand M has shown an improvement in
market share. Brand Y and Brand Z has decrease in market share, where as all other cate gories
remains the same. This shows that Brand A and M has gained market share at the cost of Y and
Z.
There are two types of panels: (a) True panel (b) Omnibus panel.
(a) True panel: This involves repeat measurement of the same variables. Example: Perception
towards frozen peas or iced tea. Each member of the panel is examined at a different time,
to arrive at a conclusion on the above subject.
(b) Omnibus panel: In omnibus panel too, a sample of elements is being selected and
maintained, but the information collected from the member varies. At a certain point of
time, the attitude of panel members "towards an advertisement" may be measured. At
some other point of time the same panel member may be questioned about the "product
performance".

Advantages of Panel Data

(a) We can find out what proportion of those who bought our brand and those who did not.
This is computed using the brand switching matrix.
(b) The study also helps to identify and target the group which needs promotional effort.
(c) Panel members are willing persons, hence a lot of data can be collected. This is because
becoming a member of a panel is purely voluntary.

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