This presentation is on Measurement and it's scales. There are four different types of scales of measurement, namely, Nominal, Ordinal, Interval and Ratio

1. Measurement
Scales
USRA HASAN
M.SC. MEDICAL PHYSIOLOGY
A13156217001

2. Contents
 Introduction
 Measurement
 Measurement scales
− Nominal scale
− Ordinal scale
− Interval scale
− Ratio scale
 Reference

3. Introduction
 The process of assigning numbers to objects or
observations is referred as measurement.
 The level of measurement is a function of the rules
under which the numbers are assigned.
 Properties like weight, height, etc., can be measured
directly with some standard unit of measurement and
are easy to determine.
 But it is not that easy to measure properties like
motivation to succeed, ability to stand stress and the
like.

4. Measurement
 Measurement is a process of mapping aspects of a
domain onto other aspects of a range according to
some rule of correspondence.
where,
in terms of set theory,
range may refer to some set and domain may refer to
some other set.

5. For example
 In case we are to find the male to female attendance ratio
while conducting a study of persons who attend some
show, then we may tabulate those who come to the show
according to sex.
 In terms of set theory,
this process is one of mapping the observed physical
properties of those coming to the show (the domain) on
to a sex classification (the range).
 The rule of correspondence is:
If the object in the domain appears to be male, assign to
“0” and if female assign to “1”.

6. Measurement Scales
 Scales of measurement can be considered in terms of
their mathematical properties, classified into:
1. Nominal scale ( least powerful )
2. Ordinal scale
3. Interval scale
4. Ratio scale ( most powerful )

7. Nominal Scale
 Simply a system of assigning number symbols to events in order
to label them.
 It provides convenient ways of keeping track of people, objects
and events.
 Mode is used as the measure of central tendency.
 It simply describes differences between things by assigning
them to categories.
 Nominal data are counted data.
 It is widely used in surveys and other ex-post-facto research
when data are being classified by major sub-groups of the
population.

8. For example
The Assignment Of Numbers Of Basketball
Players In Order To Identify Them.
 Such numbers cannot be considered to be associated
with an ordered scale for their order is of no
consequence, the numbers are just convenient labels
for the particular class of events and as such have no
quantitative value.
 One cannot usefully average the numbers on the back
of a group of football players and come up with a
meaningful value.

9. Ordinal Scale
 places events in order, but there is no attempt to make the
intervals of the scale equal in terms of some rule.
 It only permit the ranking of items from highest to lowest
and have no absolute values, and the real differences
between adjacent ranks may not be equal.
 It implies a statement of ‘greater than’ or ‘less than’ an
equality statement is also acceptable, without stating how
much greater or less.
 The appropriate measure of central tendency is the median.
 Rank orders represent ordinal scales and are frequently
used in research relating to qualitative phenomena.

10. For example
 A student’s rank in his graduation class involves the
use of an ordinal scale.
If Ram’s position in his class is 10 and
Mohan’s position is 40.
 It cannot be said that Ram’s position is four times as
good as that of Mohan.
Ranking an experience as a “9”, on a scale of
1 to 10.
 It signifies that the experience is higher than an
experience ranked as 6.

11. Interval Scale
 intervals are adjusted in terms of some rule that has been
established as a basis for making the units equal.
 Interval scales can have an arbitrary zero but lack of a
true zero.
 Therefore, it does not have the capacity to measure the
complete absence of a trait or characteristic.
 It provide more powerful measurement than ordinal
scales for interval scale also incorporates the concept of
equality of interval.
 Mean is the appropriate measure of central tendency.

12. For example
The Fahrenheit Scale.
 An increase in temperature from 30° to 40° involves
the same increase in temperature as an increase from
60° to 70°.
 But one cannot say that the temperature of 60° is twice
as warm as the temperature of 30° because both
numbers are dependent on the fact that the zero on
the scale is set arbitrarily at the temperature of the
freezing point of water.
 The ratio of the two temperatures, 30° and 60°, means
nothing because zero is an arbitrary point.

13. Ratio scale
 possesses the qualities of nominal, ordinal and interval
scales.
 It has an absolute zero, point where none of the quality
being measured exists.
 It represents the actual amounts of variables, measures
of physical dimensions such as weight, height, distance, etc.
 Multiplication and division can be used with this scale but
not with other scales.
 Geometric and harmonic means can be used as measures
of central tendency and coefficients of variation may also be
calculated.
 It permits comparisons.

14. For example
A Centimetre Scale
 the zero point on a centimetre scale indicates the
complete absence of length or height.
24 Hour Clock
 It has an absolute 0 (midnight), so we can say that 14
o’clock is twice as long from midnight as 7 o’clock.

15. Reference
 Research Methodology, Methods And
Techniques
− C.R. Kothari