### Scatter Graphs

#### Definition

A scatter graph is a diagram which compares two sets of data. Scatter graphs are also widely referred to as scatter plots or scatter diagrams. Drawing a scatter graph gives a visual representation of the relationship between these two sets of data. Usually, the $x$-axis will represent the independent variable and the $y$-axis will represent the dependent variable.

#### Worked Example

###### Worked Example

A gym records the height and weight of ten members.

 Height (cm) Weight (kg) $183$ $190$ $167$ $178$ $182$ $171$ $180$ $192$ $181$ $179$ $63$ $85$ $87$ $63$ $66$ $58$ $60$ $65$ $69$ $66$

Draw a scatter graph to represent this information.

###### Solution

Here, we put the height on the $x$-axis. To draw the first point, go along the $x$-axis until you get to $183$cm. Then take a direct line upwards until you hit $63$kg. Repeat this for the other points.

To further analyse this data see Types of Correlation and Strength of Correlation.

#### Common Mistakes

You will notice above that the axes do not start at zero. If they were to start at zero, the graph would look like this.

This graph is much more difficult to analyse than the graph with the axes cut to start at $165$ and $55$ so it is important that your graph contains all the points, but as little extra blank space as possible. Learn more here.