The Box, Diamond and Dot plot uses boxes, diamonds and dots to form a schematic of a set of observations. The schematic can give you insight into the shape of the distribution of observations. Some Box, Diamond and Dot plots have several schematics. These side-by-side plots can also help you see if the distributions have the same average value and the same variation in values. 

The plot always displays dots. They are located vertically at the value of the observations shown on the vertical scale. (The dots are 'jittered' horizontally by a small random ammount to avoid overlap).

The plot can optionally display boxes and diamonds. Boxes summarize information about the quartiles of the variable's distribution. Diamonds summarize information about the moments of the variable's distribution. The BOX and DIAMOND buttons at the bottom of the graph control whether boxes or diamonds (or both) are displayed.

The box plot is a simple schematic of a variable's distribution. The schematic gives you information about the shape of the distribution of the observations. The schematic is especially useful for determining if the distribution of observations has a symmetric shape. If the portion of the schematic above the middle horizontal line is a reflection of the part below, then the distribution is symmetric. Otherwise, it is not.

In the box plot, the center horizontal line shows the median, the bottom and top edges of the box are at the first and third quartile, and the bottom and top lines are at the 10th and 90th percentile. Thus, half the data are inside the box, half outside. Also, 10% are above the top line and another 10% are below the bottom line. The width of the box is proportional to the total number of observations.

The diamond plot is another schematic of the distribution, but it is based on the mean and standard deviation. The center horizontal line is at the mean, and the top and bottom points of the diamond are one standard deviation away from the mean. The width is proportional to the number of observations. The diamond is always symmetric, regardless of whether the distribution is symmetric.

In side-by-side plots, both the box plot and diamond plot can be used to see if the distributions have the same central tendency and the same variation. If the several medians, as well as the several means, are all about the same, then the central tendency for each distribution is about the same. If the diamonds are all approximately the same size vertically, and if the boxes are also all about the same size vertically, then the distributions have about the same variation.

