Finding Median for Grouped Data When Class Intervals Are Given
If median of ...
Question
If median of the following frequency distribution is 35 then find the value of x.
Class interval
0-10
10-20
20-30
30-40
40-50
50-60
60-70
Frequency
2
3
x
6
5
3
2
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Solution
Class interval
frequency
cumulitative frequency
0−10
2
2
10−20
3
5
20−30
x
5+x
30−40
6
11+x
40−50
5
16+x
50−60
3
19+x
60−70
2
21+x
Total frequency= 21+x
=> N=21+x => N2=21+x2 So; CF corresponding to this is 11+x And class corresponds to this is 30−40 So, l=30 , F=5+x , f=6 and h=10 Median=l+⎛⎜
⎜
⎜⎝N2−Ff⎞⎟
⎟
⎟⎠×h => 35=30+⎛⎜
⎜
⎜⎝21+x2−5−x6⎞⎟
⎟
⎟⎠×10 => x=5