Research Methodology - Dr. Krishan K. Pandey

Measurement and Scaling Techniques 81
Rank order 2 3 1 4
Mp 0.5375 0.4625 0.5450 0.4550
Zj 0.09 (–).09 0.11 (–).11
Rj 0.20 0.02 0.22 0.00
Comparing the total number of preferences for each of the four proposals, we find that C is the
most popular, followed by A, B and D respectively in popularity. The rank order shown in the above
table explains all this.
By following the composite standard method, we can develop an interval scale from the pairedcomparison
ordinal data given in the above table for which purpose we have to adopt the following
steps in order:
(i) Using the data in the above table, we work out the column mean with the help of the
formula given below:
bg b g
b g
C N
M p
nN
=
+ . 5 165 + . 5 100
=
4 100
= . 5375
where
M p = the mean proportion of the columns
C = the total number of choices for a given suggestion
n = number of stimuli (proposals in the given problem)
N = number of items in the sample.
The column means have been shown in the M p row in the above table.
(ii) The Z values for the M p are secured from the table giving the area under the normal curve.
When the M p value is less than .5, the Z value is negative and for all M p values higher than
.5, the Z values are positive. * These Z values are shown in Z j row in the above table.
(iii) As the Z j values represent an interval scale, zero is an arbitrary value. Hence we can
eliminate negative scale values by giving the value of zero to the lowest scale value (this
being (–).11 in our example which we shall take equal to zero) and then adding the absolute
value of this lowest scale value to all other scale items. This scale has been shown in R j
row in the above table.
Graphically we can show this interval scale that we have derived from the paired-comparison
data using the composite standard method as follows:
D B A C
0.0 0.1 0.2 0.3 0.4
Fig. 5.2
* To use Normal curve area table for this sort of transformation, we must subtract 0.5 from all Mp values which exceed
.5 to secure the values with which to enter the normal curve area table for which Z values can be obtained. For all M p values
of less than . 5 we must subtract all such values from 0.5 to secure the values with which to enter the normal curve area table
for which Z values can be obtained but the Z values in this situation will be with negative sign.