Free Outlier Detection Calculator
Detect potential outliers using the IQR method by checking if a value falls outside the inner fences (Q1 - 1.5*IQR, Q3 + 1.5*IQR).
IQR
40.0000
Lower Fence-30.0000
Upper Fence130.0000
Outside Fences? (1=yes)0
Distance Beyond Fence0.0000
IQR vs Value to Test
How to Detect Outliers Using the IQR Method
Formula
IQR = Q3 - Q1
Lower Fence = Q1 - 1.5 * IQR
Upper Fence = Q3 + 1.5 * IQR
Values below the lower fence or above the upper fence are flagged as potential outliers. The 1.5 multiplier is Tukey's convention. Using 3.0 instead identifies extreme outliers.
Example Calculation
Q1 = 30, Q3 = 70. Is 95 an outlier?
- 01IQR = 70 - 30 = 40
- 02Lower fence = 30 - 1.5*40 = 30 - 60 = -30
- 03Upper fence = 70 + 1.5*40 = 70 + 60 = 130
- 0495 is between -30 and 130, so it is NOT an outlier
- 05It would need to exceed 130 to be flagged
Frequently Asked Questions
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