How to use it
- Paste or type your numbers.
- Pick the quartile method if your course or software specifies one.
- Read the plot and the five-number summary below it.
How it works
The data are sorted and split at the median. Q1 and Q3 are the medians of the lower and upper halves (or interpolated positions, depending on the method). The IQR is Q3 − Q1. Fences are placed 1.5 × IQR beyond the quartiles; values outside are drawn as circles, and each whisker ends at the most extreme value inside the fences.
Worked example
For 1, 2, 3, 4, 5, 6, 100 with the exclusive method: Q1 = 2, median = 4, Q3 = 6, IQR = 4. The upper fence is 6 + 6 = 12, so 100 is an outlier and the upper whisker stops at 6.
Tips
- The plot axis runs from the smallest to the largest value, so one extreme outlier squeezes the box. Check the numbers beside the plot.
- Very small samples make box plots unreliable; consider showing the raw points as well.