Scale Parameter
A scale parameter is related to the
dispersion parameter
and is given by
- Normal
![{{\sigma} = \sqrt{\phi}}](images/fiteq70.gif)
- Inverse Gaussian
![{{\sigma} = \sqrt{\phi}}](images/fiteq70.gif)
- Gamma
![{{\nu} = 1 / \phi}](images/fiteq71.gif)
- Poisson
- 1
- Binomial
- 1
The scale parameter is 1 for
Poisson and binomial distributions.
SAS/INSIGHT software provides different
scale parameter estimates for normal,
inverse Gaussian, and gamma distributions:
- MLE
- the maximum-likelihood estimate
- Deviance
- the mean deviance
- Pearson
- the mean Pearson
![\chi^2](images/fiteq72.gif)
- Constant
- the value in the Constant entry field
When maximum-likelihood estimation is used,
the Hessian H and the gradient u
also include the term for the scale parameter.
![](../../common/images/note.gif)
Note | You can request an exponential distribution for the response variable by
specifying a gamma distribution with scale parameter set to 1. |
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.