What will be the median of the following data?
Class | 0-10 | 10-20 | 20-30 | 30-40 | 40-50 | 50-60 | 60-70 |
Frequency | 3 | 4 | 5 | 6 | 3 | 2 | 1 |
50
60
30
80
Option (c) 30
The given data table is,
Class | 0-10 | 10-20 | 20-30 | 30-40 | 40-50 | 50-60 | 60-70 |
Frequency | 3 | 4 | 5 | 6 | 3 | 2 | 1 |
From the given table, we have the frequency distribution table as,
class | Frequency | Mid value | cumulative frequency | |
0-10 | 3 |
5 |
3 | 15 |
10-20 | 4 | 15 | 7 | 60 |
20-30 | 5 | 25 | 12 | 125 |
30-40 | 6 | 35 | 18 | 210 |
40-50 | 3 | 45 | 21 | 135 |
50-60 | 2 | 55 | 23 | 110 |
60-70 | 1 | 65 | 24 | 65 |
We know the general formula for median of grouped data is,
Where,
=lower limit of the median class,
=size of the median class,
= frequency of the median class,
= sum of frequencies and
=cumulative frequency of the class just preceding the median class.
We have,
Here, the cumulative frequency just greater than 12 is 18 and the corresponding class is 30-40
Therefore, the median class is 30-40.
Calculating the median, we get,
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