A Box Plot, also known as a Box and Whisker Diagram, is a basic graphing tool that displays the spread, distribution, and centering of a continuous data set.
A Box Plot provides a 5 point summary of the data:
- The box represents the middle 50% of the data.
- The median is the point where 50% of the data is above it and 50% below it. (Or left and right depending on orientation).
- The 25th quartile is where, at most, 25% of the data fall below it.
- The 75th quartile is where, at most, 25% of the data is above it.
- The "whiskers" cannot extend any further than 1.5 times the length of the inner quartiles. If you have data points outside this they will show up as outlier.