Page 141 - DCOM203_DMGT204_QUANTITATIVE_TECHNIQUES_I

Quantitative Techniques – I

Notes
Example: Determine the interquartile range and percentile range of the following
distribution:
Class Intervals : 11 13 13 15 15 17 17 19 19 21 21 23 23 25
Frequency : 8 10 15 20 12 11 4

Solution:

Class Intervals Frequency Less than c . .
f
11 13 8 8
13 15 10 18
15 17 15 33
17 19 20 53
19 21 12 65
21 23 11 76
23 25 4 80
1. Calculation of Interquartile Range
Calculation of Q
1
N 80
Since 20, the first quartile class is 15 - 17
4 4
= 15, = 15, h = 2 and C = 18
Q 1 Q 1
20 18
Hence, 1 15 2 15.27
15
Calculation of Q
3
3N 3 80
Since 60, the third quartile class is 19 - 21
4 4

= 19, = 12, h = 2 and C = 53
Q 3 Q 3
60 53
.
Hence, 3 19 2 20 17
12
Thus, the interquartile range = 20.17 – 15.27 = 4.90
2. Calculation of Percentile Range
Calculation of P
10
10N 10 80
Since, 8, P lies in the class interval 11 – 13
100 100 10
= 11, = 8, h = 2 and C = 0
P 10 P 10

8 0
Hence, 10 11 2 13
8

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