IQR Method Method

What is the IQR Method?

The IQR Method (Interquartile Range Method) is a statistical technique for identifying outliers based on the spread of the middle 50% of the data.

How It Works

1. Calculate Q1 (25th percentile) and Q3 (75th percentile)
2. Compute IQR = Q3 - Q1
3. Define boundaries:
   • Lower: Q1 - 1.5 * IQR
   • Upper: Q3 + 1.5 * IQR
4. Values outside boundaries are outliers

Advantages

• Simple: Easy to calculate and understand
• Robust: Not affected by extreme outliers
• No Distribution Assumptions: Works with any distribution

When to Use

• Exploratory data analysis
• Preprocessing before ML modeling
• Quality control of measurements

Related Terms

• Z-Score Method: Alternative using standard deviations
• Outlier Detection: The broader process