Interquartile Range Calculator

The IQR spans the middle half of the data, from the 25th to the 75th percentile. Unlike the range or standard deviation, it ignores extreme values entirely — one billionaire in the sample can't move it — which is why box plots are built on it.

Tukey's convention flags values beyond 1.5 IQRs outside the quartiles as outliers — the whisker limit on box plots. It's a screening rule, not a verdict: flagged points deserve investigation (data error? genuine extreme?), not automatic deletion.