5 Simple Steps to Calculate IQR in Excel

The Interquartile Range (IQR) is a measure of statistical dispersion, which can be particularly useful to understand the spread of a dataset by focusing on the middle 50% of observations. Here's a step-by-step guide on how to calculate the IQR in Microsoft Excel.

1. Sort Your Data

Before calculating the IQR, you first need to sort your data in ascending order:

• Select the cell range containing your data.
• Go to the “Data” tab on the Excel ribbon.
• Click on “Sort & Filter” and choose “Sort Smallest to Largest.”

Sorting ensures that the data values are in order, making it easier to identify the quartiles.

2. Find the First Quartile (Q1)

Once your data is sorted:

• Determine if the dataset size (n) is odd or even:
• If n is odd, Q1 is the median of the first half of the data points.
• If n is even, Q1 is the average of the two middle numbers in the first half.

3. Calculate the Third Quartile (Q3)

Similar to finding Q1:

• If n is odd, Q3 is the median of the second half of the data points.
• If n is even, Q3 is the average of the two middle numbers in the second half.

4. Compute the IQR

Now, subtract Q1 from Q3:

• Use Excel’s formula: =Q3 - Q1 to get your IQR.

5. Display the Results

To make the IQR calculation easier to see:

• Create labels for Q1, Q3, and IQR next to your data.
• Enter the respective values in the cells next to these labels.

📊 Note: Using labels and the values in separate cells allows for easier future referencing or when calculating other statistical measures.

Calculating the IQR in Excel is not just about following steps, it's about understanding the data distribution. By focusing on the middle 50% of the data, you get a sense of variability that isn't influenced by extreme values, which is particularly useful in identifying outliers or in preparing data for further analysis. This method also provides insights into the dataset's skewness, helping you to make more informed decisions or observations about your data.