Q-Q Plots and Normal Q-Q Plots

Click the Home | New Graph | Statistical | Q-Q Plot or the Home | New Graph | Statistical | Normal Q-Q Plot command to plot a Q-Q plot. A Q-Q plot is a type of probability plot which compares the probability distribution of two data sets by plotting their quantiles against each other. Each point plotted on the Q-Q plot represents the same quantile in each data set. If the two distributions being compared have similar distributions, the points will approximately lie on the line y=x. If the distributions are linearly related, the points will lie on a line, but not necessarily the y=x line.

Click the Q-Q Plot or Normal Q-Q Plot buttons to create the desired plot type.

 

The Normal Q-Q Plot plots the distribution of a single data set against the normal distribution. To change a Q-Q plot to a Normal Q-Q plot, change either the X column or Y column property on the Property Manager Plot page to None.

 

The y=x line is also plotted on both the Q-Q plot and the normal Q-Q plot.

 


Q-Q plots show data as symbols with a y=x line

This plot compares two data sets that are closely related,

so the data fall almost always along the y=x line.

 

Creating a Q-Q Plot or Normal Q-Q Plot

To create a new Q-Q plot or normal Q-Q plot:

  1. Click the Home | New Graph | Statistical | Q-Q Plot or the Home | New Graph | Statistical | Normal Q-Q Plot command.

  2. Select a data file in the Open Worksheet dialog. You can select a new data file or you can select an open data file in the Open worksheets section.

  3. Click the Open button. A Q-Q plot or normal Q-Q plot is created using the default properties.

 

Editing an Q-Q Plot or Normal Q-Q Plot

To change the features of a Q-Q plot or a normal Q-Q plot, click once on the plot in either the plot window or the Object Manager to select it. The properties of the selected Q-Q plot are displayed in the Property Manager.

 

Click the following tabs in the Property Manager to change different properties:

Plot

Data Limits

Labels

Symbol

Line

 

Graph Properties

The graph properties contain the following pages in the Property Manager.

Title

Line

Fill

 

 

See Also

Fit Curves

Standard Axes

Graph Title

Graph Wizard

Line/Scatter Plots

Histograms