QUARTILES—HAND CALCULATIONS AND THE SOFTWARE OUTPUT

Range, Quartiles, Interquartile range, and the Software Output (SPSS, Excel, and Python)

September 25, 2025

The Range and the Inter-Quartile Range (IQR) are the measures that describe the spread of data.

EXAMPLE  4

A tracking sheet includes the years of relevant job experience for various posts.

5, 7, 4, 6, 8, 9, 4

Let’s arrange the data in ascending order.

4
4
5
6
7
8
9

RANGE

The range of a data set is the difference between the highest (maximum) and lowest (minimum) values.

Range = Maximum value - Minimum value

Range = 9 - 4 = 5 years

QUARTILES

The 2nd Quartile (Q2) or the middle quartile is the median. It is the middle value that divides the data into two equal parts.

4
4
5
6
7
8
9
Median = 6

The 1st Quartile (Q1) or the lower quartile (QL) separates the lower quarter of values from the rest of the values. This is the value at the middle point of the first half of the data.

4
4
5
6
Lower Quartile (QL) = 4.5

The 3rd Quartile (Q3) or the upper quartile (QU) separates the upper quarter of values from the rest of the values. This is the value at the middle point of the second half of the data.

6
7
8
9
Upper quartile (QU) = 7.5

INTER QUARTILE RANGE (IQR)

It is the difference between the upper quartile (Q3 or QU) and the lower quartile (Q1 or QL)

IQR = QU - QL

IQR = 7.5 - 4.5 = 3 years

QUARTILES IN SOFTWARE OUTPUT

The table summarizes the quartile values calculated by the pre-defined functions of computer software.

Computer Software Q1 Q2 Q3
SPSS (Tukey's Hinges) 4.5 6 7.5
Excel (Quartile) 4.5 6 7.5
Python (Quantile) 4.5 6 7.5

EXAMPLE  5

Values of the open positions variable on a Job recruitment sheet are:

6, 7, 5, 12, 9, 10

Let’s arrange the data in ascending order.

5
6
7
9
10
12

RANGE

Range = Maximum value - Minimum value

Range = 12 - 5 = 7

QUARTILES

The 2nd Quartile (Q2) or the middle quartile is the median

5
6
7
9
10
12
Median = 8

The 1st Quartile (Q1) or the lower quartile (QL)

5
6
7
Lower Quartile (QL) = 6

The 3rd Quartile (Q3) or the upper quartile (QU)

9
10
12
Upper quartile (QU) = 10

INTER QUARTILE RANGE (IQR)

It is the difference between the upper quartile (Q3 or QU) and the lower quartile (Q1 or QL)

IQR = QU - QL

IQR = 10 - 6 = 4

QUARTILES IN SOFTWARE OUTPUT

The table summarizes the quartile values calculated by the pre-defined functions of computer software.

Computer Software Q1 Q2 Q3
SPSS (Tukey's Hinges) 6 8 10
Excel (Quartile) 6.25 8 9.75
Python (Quantile) 6.25 8 9.75

 

 


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