,k.hgfi.ikn,

1. DECILES OF GROUPED
DATA

2. The decile of group data
Deciles are those values that
divide the total frequency into
10 equal parts. The kth decile
denoted by 𝐷𝑘 is computed as
follows

3. Formula to be used:
𝐷𝑘=LB+(
𝑘𝑁
10
-cf)i
𝑓𝐷𝐾

4. Where:
 LB= lower boundary of the Dk class
 N= is the total frequency.
𝑐𝑓𝑏= is the cumulative frequency of the
class
before the 𝐷𝑘class.
𝐹𝑑𝑘= is the frequency of the 𝐷𝑘 class.
I= is the size of class interval.
k= nth decile, where n=1,2,3,......,9

5. Example:
 Calculate the 𝐷7 of the mathematics test scores of 50
students.
Scores Frequency
46-50 4
41-45 8
36-40 11
31-35 9
26-30 12
21-25 6

6. Sol’n
Class
Interval
Scores
Frequency LB CF
46-50 4 45.5 50
41-45 8 40.5 46
36-40 11 35.5 38
31-35 9 30.5 27
26-30 12 25.5 18
21-25 6 20.5 6
n= 30

7. 𝐷7
7𝑁
10
=
7(50)
10
=
350
10
= 35
𝐷7=35.5+(
35−27
11
)5
= 39.14
The 𝐷7 class is the class interval 36-40.

8. Let’s try it!
Calculate for 𝐷2 , 𝐷3 and 𝐷4