4. Percentile Example
1. Calculate Percentiles-20 from the following grouped data
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`
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`
3. Calculate Percentiles-20 from the following grouped data
Class | Frequency | 2 - 4 | 3 | 4 - 6 | 4 | 6 - 8 | 2 | 8 - 10 | 1 |
Solution:
Class | Frequency `f` | `cf` | 2 - 4 | 3 | 3 | 4 - 6 | 4 | 7 | 6 - 8 | 2 | 9 | 8 - 10 | 1 | 10 | --- | --- | --- | | n = 10 | -- |
Here, `n = 10`
`P_20` class :
Class with `((20n)/100)^(th)` value of the observation in `cf` column
`=((20*10)/100)^(th)` value of the observation in `cf` column
`=(2)^(th)` value of the observation in `cf` column
and it lies in the class `2 - 4`.
`:. P_20` class : `2 - 4`
The lower boundary point of `2 - 4` is `2`.
`:. L = 2`
`P_20 = L + ((20 n)/100 - cf)/f * c`
`=2 + (2 - 0)/3 * 2`
`=2 + (2)/3 * 2`
`=2 + 1.3333`
`=3.3333`
4. Calculate Percentiles-70 from the following grouped data
Class | Frequency | 0 - 2 | 5 | 2 - 4 | 16 | 4 - 6 | 13 | 6 - 8 | 7 | 8 - 10 | 5 | 10 - 12 | 4 |
Solution:
Class | Frequency `f` | `cf` | 0 - 2 | 5 | 5 | 2 - 4 | 16 | 21 | 4 - 6 | 13 | 34 | 6 - 8 | 7 | 41 | 8 - 10 | 5 | 46 | 10 - 12 | 4 | 50 | --- | --- | --- | | n = 50 | -- |
Here, `n = 50`
`P_70` class :
Class with `((70n)/100)^(th)` value of the observation in `cf` column
`=((70*50)/100)^(th)` value of the observation in `cf` column
`=(35)^(th)` value of the observation in `cf` column
and it lies in the class `6 - 8`.
`:. P_70` class : `6 - 8`
The lower boundary point of `6 - 8` is `6`.
`:. L = 6`
`P_70 = L + ((70 n)/100 - cf)/f * c`
`=6 + (35 - 34)/7 * 2`
`=6 + (1)/7 * 2`
`=6 + 0.2857`
`=6.2857`
5. Calculate Percentiles-20 from the following grouped data
Class | Frequency | 10 - 20 | 15 | 20 - 30 | 25 | 30 - 40 | 20 | 40 - 50 | 12 | 50 - 60 | 8 | 60 - 70 | 5 | 70 - 80 | 3 |
Solution:
Class | Frequency `f` | `cf` | 10 - 20 | 15 | 15 | 20 - 30 | 25 | 40 | 30 - 40 | 20 | 60 | 40 - 50 | 12 | 72 | 50 - 60 | 8 | 80 | 60 - 70 | 5 | 85 | 70 - 80 | 3 | 88 | --- | --- | --- | | n = 88 | -- |
Here, `n = 88`
`P_20` class :
Class with `((20n)/100)^(th)` value of the observation in `cf` column
`=((20*88)/100)^(th)` value of the observation in `cf` column
`=(17.6)^(th)` value of the observation in `cf` column
and it lies in the class `20 - 30`.
`:. P_20` class : `20 - 30`
The lower boundary point of `20 - 30` is `20`.
`:. L = 20`
`P_20 = L + ((20 n)/100 - cf)/f * c`
`=20 + (17.6 - 15)/25 * 10`
`=20 + (2.6)/25 * 10`
`=20 + 1.04`
`=21.04`
5. Calculate Percentiles-70 from the following grouped data
Class | Frequency | 20 - 25 | 110 | 25 - 30 | 170 | 30 - 35 | 80 | 35 - 40 | 45 | 40 - 45 | 40 | 45 - 50 | 35 |
Solution:
Class | Frequency `f` | `cf` | 20 - 25 | 110 | 110 | 25 - 30 | 170 | 280 | 30 - 35 | 80 | 360 | 35 - 40 | 45 | 405 | 40 - 45 | 40 | 445 | 45 - 50 | 35 | 480 | --- | --- | --- | | n = 480 | -- |
Here, `n = 480`
`P_70` class :
Class with `((70n)/100)^(th)` value of the observation in `cf` column
`=((70*480)/100)^(th)` value of the observation in `cf` column
`=(336)^(th)` value of the observation in `cf` column
and it lies in the class `30 - 35`.
`:. P_70` class : `30 - 35`
The lower boundary point of `30 - 35` is `30`.
`:. L = 30`
`P_70 = L + ((70 n)/100 - cf)/f * c`
`=30 + (336 - 280)/80 * 5`
`=30 + (56)/80 * 5`
`=30 + 3.5`
`=33.5`
This material is intended as a summary. Use your textbook for detail explanation. Any bug, improvement, feedback then
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