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The Interquartile Range (IQR) in SPSS can be calculated by first obtaining the data set and then selecting the “Descriptives” option under the “Analyze” tab. From there, select the variable of interest and click on the “Options” button. In the options menu, check the box next to “IQR” and click “Continue” and then “OK”. This will generate a new variable in the output window which represents the IQR. The IQR is calculated by taking the difference between the 75th percentile (Q3) and the 25th percentile (Q1) of the data set.
In statistics, the interquartile range represents the spread of the middle 50% of values in a dataset.
It is calculated as the difference between the 75th percentile (Q3) and the 25th percentile (Q1) of a dataset.
The easiest way to calculate the interquartile range of a dataset in SPSS is to use Analyze > Descriptive Statistics > Explore.
The following example shows how to do so in practice.
Example: How to Calculate Interquartile Range in SPSS
Suppose we have the following dataset in SPSS that shows the exam scores received by various students in some class:
Suppose that we would like to calculate the interquartile range for the exam scores.
To do so, click the Analyze tab, then click Descriptive Statistics, then click Explore:
In the new window that appears, drag Exam_Score to the Dependent List panel:
Then click the Statistics button. In the new window that appears, check the box next to Percentiles and then click the button next to Quartiles:
Then click Continue. Then click OK.
The following output will appear:
In the Percentiles table, we can see that the value at the 25th percentile is 86 and the value at the 75th percentile is 96.
Thus, here is how the interquartile range was calculated:
- IQR = 75th percentile – 25th percentile
- IQR = 96 – 86
- IQ = 10
This matches the value shown in the output.
Related:
Additional Resources
The following tutorials explain how to perform other common tasks in SPSS: