Re: why use pi^2/3 replace of error variance 1 in binomial analysis?

The PROBIT transformation maps a probability to an underlying scale
using the Standard Normal distribution which has a variance of 1.

The LOGIT transformation works in the same way, but is based on a
Logistic distribution which has a variance of pi^2/3.

Thus, with a logit link, the implicit residual variance on the
underlying scale is the variance of the logistic distribution.
This defines the scale on which the other components are estimated.

On Tue, 2009-03-31 at 16:41 +0800, luansheng wrote:
> In the p333 of asreml 3 user guide, it is about an analysis of footrot
> as a binomial variable using the logistic link. In this example, using
> pi^2/3 replace of error variance 1. I don't know the reason, anyone
> tell me? thanks!
>
>
> --
> Luan sheng
> ----------------------------------------
> Yellow Sea Fisheries Research Institute
> Chinese Academy of Fisheries Sciences
> Nanjing Road 106
> Qingdao 266071
> China
> luansheng_at_gmail.com
> luansheng_at_ysfri.ac.cn
> ----------------------------------------
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