A bubble chart is a variation on a scatter chart, but which uses the size of the data point to depict an additional variable. Like in a scatter chart, the data points are plotted on the x and y axes according to two variables. However, the size of the bubble is determined by a third variable, so that larger values are shown as bigger bubbles.
A bubble chart can be a good choice for creating an attractive chart that gives information on three different variables. Bubble charts take a bit of time to absorb and understand, so they should be used sparingly and in accordance with the audience’s interest level.
A scatter chart uses dots to represent a data point according to two different numeric variables plotted on the horizontal and vertical axes. Scatter charts are useful for determining whether any relationships exist between the two variables.
Scatter charts are useful for showing larger data sets and they help us to identify any correlations as well as see any outliers. However, more complex relationships can be difficult to interpret, and so for presentation purposes, it might be more appropriate to process the data first and include trend lines or use a different chart type (such as a candlestick chart if you wish to preserve some statistical information).