Chapter Contents |
Previous |
Next |

QQPLOT Statement |

The QQPLOT statement creates a quantile-quantile plot (Q-Q plot), which compares ordered values of a variable with quantiles of a specified theoretical distribution such as the normal. If the data distribution matches the theoretical distribution, the points on the plot form a linear pattern. Thus, you can use a Q-Q plot to determine how well a theoretical distribution models a set of measurements.

You can specify one of the following theoretical distributions with the QQPLOT statement:

- beta
- exponential
- gamma
- three-parameter lognormal
- normal
- two-parameter Weibull
- three-parameter Weibull

You can use options in the QQPLOT statement to

- specify or estimate parameters for the theoretical distribution
- display a reference line corresponding to specific location and scale parameters for the theoretical distribution
- request graphical enhancements

**Note:** Q-Q plots are similar to probability plots, which
you can create with the PROBPLOT statement
(see Chapter 9, "PROBPLOT Statement").
Q-Q plots are preferable for graphical estimation of distribution
parameters and capability indices, whereas
probability plots are preferable for
graphical estimation of percentiles.

Chapter Contents |
Previous |
Next |
Top |

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.