[Rasch] Use of e in the Rasch model

Kenji Yamazaki yk0271 at yahoo.co.jp
Tue Sep 6 09:17:49 EST 2011

```Hi Thomas,  Thank you very much for your explanation. My background is psychology, and I learned basics of calculus when I was in high school.  So, I can understand the concept of derivatives, but I did not know the derivative of f(x)=exp(X) is equal to f ' (x)=exp(x).  That is very useful.  So, is the use of exp in the Rasch model driven by this practicality?  Is the function f(x)=exp(x) the only one whose derivative is equal to itself? Kenji
--- On Tue, 2011/9/6, Thomas Salzberger <thomas.salzberger at gmail.com> wrote:

And, of course, the derivation of [e to the power of x] is [e to the power of x], which is very convenient.
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___________________________________
Thomas.Salzberger at gmail.com

Thomas.Salzberger at wu.ac.at

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