🚨 Outlier Calculator

Detect possible outliers using the 1.5×IQR rule and display the lower and upper fences.

📊 Statistics📐 Formula included🧠 Practice questions✓ Free

Data values

Please enter valid values.

Formula and Explanation

Detect possible outliers using the 1.5×IQR rule and display the lower and upper fences.

Concept	Formula or rule
Outlier Calculator	Lower fence = Q₁ − 1.5×IQR · Upper fence = Q₃ + 1.5×IQR

How to Use This Calculator

Enter the sample, counts, probabilities, or summary statistics requested above.
Keep paired lists in the same order and separate values with commas.
Select the correct test direction or sample/population option when available.
Press Calculate and interpret the result together with the supporting statistics.

Worked Example

Example: If Q1=5, Q3=9, IQR=4, then the fences are −1 and 15.

✓ Any value below −1 or above 15 is flagged.

Where This Is Used

School & coursework

Check homework, understand formulas, and verify step-by-step statistics exercises.

Research

Explore estimates, uncertainty, distributions, and relationships before using full statistical software.

Business & data analysis

Summarize variation, compare groups, and communicate data-driven findings clearly.

Common Mistakes to Avoid

⚠️

Automatically deleting flagged values
An outlier can be a valid and important observation.

⚠️

Using the rule on tiny datasets without judgment
Small samples may produce unstable fences.

⚠️

Confusing unusual with erroneous
Investigate the cause before excluding data.

Practice Questions

1. Q1=10, Q3=20. What is the upper fence?

Answer: 35

2. Q1=10, Q3=20. What is the lower fence?

Answer: -5

3. Should every outlier be removed?

Answer: No.

Frequently Asked Questions

Does the IQR rule prove a value is wrong?▾

No. It only flags values for review.

What is an extreme outlier?▾

Some analysts use 3×IQR fences for more extreme points.

Can a dataset have no outliers?▾

Yes.