Median
Median
Definition: Median
The median of a data set is the value in the central position, when the data set has been arranged from the lowest to the highest value.
Note that exactly half of the values from the data set are less than the median and the other half are greater than the median.
To calculate the median of a quantitative data set, first sort the data from the smallest to the largest value and then find the value in the middle. If there is an odd number of values in the data set, the median will be equal to one of the values in the data set. If there is an even number of values in the data set, the median will lie halfway between two values in the data set.
Example
Question
What is the median of \(\{10; 14; 86; 2; 68; 99; 1\}\)?
Sort the values
The values in the data set, arranged from the smallest to the largest, are
\[1; 2; 10; 14; 68; 86; 99\]Find the number in the middle
There are \(\text{7}\) values in the data set. Since there are an odd number of values, the median will be equal to the value in the middle, namely, in the fourth position. Therefore the median of the data set is \(\text{14}\).
Example
Question
What is the median of \(\{11; 10; 14; 86; 2; 68; 99; 1\}\)?
Sort the values
The values in the data set, arranged from the smallest to the largest, are
\[1; 2; 10; 11; 14; 68; 86; 99\]Find the number in the middle
There are \(8\) values in the data set. Since there are an even number of values, the median will be halfway between the two values in the middle, namely, between the fourth and fifth positions. The value in the fourth position is \(\text{11}\) and the value in the fifth position is \(\text{14}\). The median lies halfway between these two values and is therefore
\[\text{median} = \cfrac{11 + 14}{2} = \text{12.5}\]
This lesson is part of:
Statistics and Probability