1. Calculate Percentiles-20 from the following grouped data

X	Frequency
0	1
1	5
2	10
3	6
4	3

Solution:

`x`	Frequency `f`	`cf`
0	1	1
1	5	6
2	10	16
3	6	22
4	3	25
---	---	---
	n = 25	--

Here, `n = 25`

`P_20 = ((20(n+1))/100)^(th)` value of the observation

`=((20*26)/100)^(th)` value of the observation

`=(5.2)^(th)` value of the observation

`=1`

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2. Calculate Percentiles-70 from the following grouped data

X	Frequency
10	3
11	12
12	18
13	12
14	3

Solution:

`x`	Frequency `f`	`cf`
10	3	3
11	12	15
12	18	33
13	12	45
14	3	48
---	---	---
	n = 48	--

Here, `n = 48`

`P_70 = ((70(n+1))/100)^(th)` value of the observation

`=((70*49)/100)^(th)` value of the observation

`=(34.3)^(th)` value of the observation

`=13`

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