Identify statistical outliers in a data set using the standard 1.5×IQR fence method.
How It Works
How Outlier Calculator Works
After finding Q1 and Q3, the interquartile range (IQR) is multiplied by 1.5 and used to set a lower and upper "fence" — any value falling outside those fences is flagged as a statistical outlier, a widely used convention introduced by statistician John Tukey.
FAQ
Frequently Asked Questions
Does an outlier always mean the data point is an error?
Not necessarily — it just means the value sits unusually far from the rest of the data by this statistical definition. It might be a data entry mistake, or it might be a genuine, meaningful extreme value worth investigating rather than discarding.
Why 1.5 times the IQR specifically?
It's a convention that's been widely adopted since Tukey introduced it — strict enough to flag genuinely unusual values without over-flagging normal variation in most reasonably-sized data sets.
