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How to find outliers in a dataset in Excel and Google Sheets
Topic:RANK & statistical aggregatesExcel & Google Sheets
=IF(OR(B2<QUARTILE($B$2:$B$6,1)-1.5*(QUARTILE($B$2:$B$6,3)-QUARTILE($B$2:$B$6,1)),B2>QUARTILE($B$2:$B$6,3)+1.5*(QUARTILE($B$2:$B$6,3)-QUARTILE($B$2:$B$6,1))),"Outlier","Normal")Try it with your data
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Step by step
- 1Enter your data in column B (e.g., B2:B6). Lock the range with $ signs.
- 2In column C2, enter the IQR outlier formula using QUARTILE to compute Q1, Q3, and IQR.
- 3The formula flags values below Q1-1.5*IQR or above Q3+1.5*IQR as 'Outlier'.
- 4Copy the formula down column C for every data row.
Tips
- For a simpler threshold approach, flag values more than 2 standard deviations from the mean: =IF(ABS(B2-AVERAGE($B$2:$B$6))>2*STDEV($B$2:$B$6),"Outlier","Normal").
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Frequently asked
Why use 1.5 times the IQR?
This is Tukey's fence rule, a widely accepted statistical convention for defining mild outliers. Use 3*IQR for extreme outliers.
Can I highlight outliers with conditional formatting?
Yes. Apply conditional formatting to the data column using the same IQR formula as the rule, and choose a highlight color.
More on RANK & statistical aggregates
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ReferenceRANK.AVG
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