Median is a measure of central tendency that represents the middle value of a dataset when the values are arranged in ascending or descending order.
Example 1: Find the median of the given data set 60, 70, 10, 30, and 50
Solution:
Median of the data 60, 70, 10, 30, and 50 is,
Step 1: Order the given data in ascending order as:
10, 30, 50, 60, 70
Step 2: Check if n (number of terms of data set) is even or odd and find the median of the data with respective ‘n’ value.
Step 3: Here, n = 5 (odd)
Median = [(n + 1)/2]th term
Median = [(5 + 1)/2]th term = 3rd term
= 50
Example 2: Find the median of the given data set 13, 47, 19, 25, 75, 66, and 50
Solution:
Median of the data 13, 47, 19, 25, 75, 66, and 50 is,
Step 1: Order the given data in ascending order as:
13, 19, 25, 47, 50, 66, 75
Step 2: Check if n (number of terms of data set) is even or odd and find the median of the data with respective ‘n’ value.
Step 3: Here, n = 7 (odd)
Median = [(n + 1)/2]th term
Median = [(7 + 1)/2]th term = 4th term
= 47
Example 3: Find the Median of the following data.
If the marks scored by the students in a class test out of 100 are,
| Marks | 0-20 | 20-40 | 40-60 | 60-80 | 80-100 |
|---|---|---|---|---|---|
| Number of Students | 5 | 7 | 9 | 4 | 5 |
Solution:
For finding the Median we have to build a table with cumulative frequency as,
Marks 0-20 20-40 40-60 60-80 80-100 Number of Students 5 7 9 4 5 Cumulative Frequency 0+5 = 5 5+7 = 12 12+9 = 21 21+4 = 25 25+5 = 30 n = ∑fi = 5+7+9+4+5 = 30(even)
n/2 = 30/2 = 15Median Class = 40-60
Now using the formula,
Median = l + [(n/2 – cf) / f]×hComparing with the given data we get,
- l = 40
- n = 30
- f = 9
- h = 10
- cf = 12
Median = 20 + [(15 - 12)/6]×10
= 40 - (3/9) x 20
= 40 +6.6667
= 46.6667Thus, the median mark of the class test is 46.67.
Example 4: Find the median number of hours studied per week
The following table shows the distribution of the number of hours spent studying per week by a group of students:
Hours Studied (Per week) | 0 - 5 | 5 - 10 | 10 - 15 | 15 - 20 | 20 - 25 |
|---|---|---|---|---|---|
Frequency | 8 | 15 | 25 | 12 | 10 |
Solution:
For finding the Median we have to build a table with cumulative frequency as,
Hours Studied (Per week)
0 - 5
5 - 10
10 - 15
15 - 20
20 - 25
Frequency
8
15
25
12
10
Cumulative Frequency
0 + 8 = 8
8 + 15 = 23
23 + 25 = 48
48 + 12 = 60
60 + 10 = 70
n = ∑fi = 8 + 15 + 25 + 12 + 10 = 70(even)
n/2 = 70/2 = 35
Median Class = 10 - 15
Now using the formula,
Median = l + [(n/2 – cf) / f]×h
Comparing with the given data we get,
- l = 10
- n = 70
- f = 25
- h = 5
- cf = 23
Median = 10 + [(35 - 23)/25]×5
= 10 - (12/15) x 5
= 10 - (0.48) x 5
= 10 + 2.4
= 12.4Thus, the median number of hours per week is 12.4 hours.