A box plot is a graphical tool that lets you easily visually compare variation between the data sets evaluated. Also makes comparisons quickly and easily.
- First quartile (0-25%)
- Third quartile (75%)
What Can Box Plots Tell Us?
- Skewness: By looking at a box plot you can can tell if your data distribution is skewed if the line inside the box is not centered.
- Ex. Stock 4’s median is not centered, thus this data is skewed.
- Extreme values: The vertical lines (whiskers) show max and min values.
- Ex. Stock 5 tends towards larger values.
- Median: The blue horizontal line indicates the median of the group.
- 25th & 75th Percentiles: that’s the top and bottom of the box.
- Useful in visualizing most of the spread of variation.
- Ex. Stock 1 typically has the least variation.
Creating a Box Plot
Good article on how to do this in excel.
Notes on Box Plots