The median of the following data is 525. Find the missing frequency, if it is given that there are 100 observations in the data:
Class interval | Frequency | Class interval | Frequency |
0−100 | 2 | 500−600 | 20 |
100−200 | 5 | 600−700 | f2 |
200−300 | f1 | 700−800 | 9 |
300−400 | 12 | 800−900 | 7 |
400−500 | 17 | 900−1000 | 4 |
Class interval | Frequency | Cumulative frequency |
0 – 100 | 2 | 2 |
100 – 200 | 5 | 7 |
200 – 300 | f1 | 7 + f1 |
300 – 400 | 12 | 19 + f1 |
400 – 500 | 17 | 36 + f1 (F) |
500 – 600 | 20 (f) | 56 + f1 |
600 – 700 | f2 | 56 + f1 + f2 |
700 – 800 | 9 | 65 + f1 + f2 |
800 – 900 | 7 | 72 + f1 + f2 |
900 – 1000 | 4 | 76 + f1 + f2 |
N = 100 |
Given
Median =525
Then, median class = 500–600
L =500, f=20,F = 36 + f1 , h =600–500 =100
5 = 14 – f1
f1 = 14 – 5 = 9
Given
Sum of frequencies = 100
2 + 5 + f1 + 12 + 17 + 20 + f2 + 9 + 7 + 4 = 100
2 + 5 + 9 + 12 + 17 + 20 + f2 + 9 + 7 + 4 = 100
85 + f2 = 100
f2 = 100 – 85 = 15
f1 = 9 and f2 = 15