Statistics Dictionary

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Scatterplot

A scatterplot is a graphic tool used to display the relationship between two quantitative variables.

A scatterplot consists of an X axis (the horizontal axis), a Y axis (the vertical axis), and a series of dots. Each dot on the scatterplot represents one observation from a data set. The position of the dot on the scatterplot represents its X and Y values.

Consider the example below. First, a table shows the height and the weight of five starters on a high school basketball team. Then, the same data are displayed in a scatterplot.

Height, inches Weight, pounds
67 155
72 220
77 240
74 195
69 175

Each player in the table is represented by a dot on the scatterplot. The first dot, for example, represents the shortest, lightest player. From the scale on the X axis, you see that the shortest player is 67 inches tall; and from the scale on the Y axis, you see that he/she weighs 155 pounds. In a similar way, you can read the height and weight of every other player represented on the scatterplot.

Scatterplots are helpful in understanding patterns in bivariate data . For example, the above scatterplot shows that the relationship between height and weight is linear, strong, and has a positive slope.

See also:   AP Statistics Tutorial: Scatterplots | AP Statistics Tutorial: Correlation and Linearity