Page 13 - DMGT209_QUANTITATIVE_TECHNIQUES_II

Quantitative Techniques-II

Notes 4 Prescriptive (or normative) model: A prescriptive model is one which provides the norms
for the comparison of alternative solutions which result in the selection of the best
alternative (the most preferred course of action).
Example: Allocation models.

Degree of Abstraction
The following chart shows the classification of models according to the degree of abstraction:

Any three-dimensional model that looks like the real thing but is either reduced in size or scaled
up, is a physical (conic) model. These models include city planning maps, plant layout charts,
plastic model of airplane, body parts, etc. These models are easy to observe, build and describe,
but cannot be manipulated and used for prediction.
An organisation chart showing responsibility relationships is an example of graphic model. A
flow chart (or diagram) depicting the sequence of activities during the complete processing of a
product is an example of schematic model. Another example of schematic model is the Computer
programme where main features of the programme are represented by a schematic description
of steps.

Analog models are closely associated with iconic models. However, they are not replicas of
problem situations. Rather they are small physical systems that have similar characteristics and
work like an object or system it represents.

Example: Children’s toys, model rail-roads, etc.
These models might not allow direct handling or manipulation.
Mathematical (or symbolic) models represent the systems (or reality) by using mathematical
symbols and relationships. These are very precise, most abstract and can be manipulated by
using laws of mathematics. The input-output model of national economy involving several
objectives, constraints, inputs and inter-linkages between them is an example of representing a
complex system with the help of a set of equations.

Degree of Certainty

Models can also be classified according to the degree of assumed certainty. Under this classification
models are divided into deterministic versus probabilistic models.
Models in which selection of each course of action (or strategy) results in unique and known
pay-off or consequence are called deterministic models.

Example: Linear programming, transportation and assignment models.

8 LOVELY PROFESSIONAL UNIVERSITY