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rtoy / maxima

A Clone of Maxima's repo
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pdf_geometric appears to be incorrect and/or poorly documented #2654

Closed rtoy closed 2 months ago

rtoy commented 2 months ago

Imported from SourceForge on 2024-07-06 17:11:11 Created by dirkcgrunwald on 2018-02-25 03:08:16 Original: https://sourceforge.net/p/maxima/bugs/3406

When you look at the geometric distribution in almost any statistics text, the PMF(k,p) is expressed as (1-p)^(k-1) p, which, as Wikipedia points out is for the probability that the kth trial is the success. Maxima uses the alternate definition (1-p)^k k that models that there are k failures & then success.

This should be more clearly stated in the documentation; it's counter to almost any statistics / probability text I have checked, all of which rely on the "kth trial is success" definition.

rtoy commented 2 months ago

Imported from SourceForge on 2024-07-06 17:11:12 Created by robert_dodier on 2018-03-04 04:24:48 Original: https://sourceforge.net/p/maxima/bugs/3406/#68c0

rtoy commented 2 months ago

Imported from SourceForge on 2024-07-06 17:11:16 Created by robert_dodier on 2018-03-04 04:24:49 Original: https://sourceforge.net/p/maxima/bugs/3406/#113a

I've pushed commit ce58ebd to improve the documentation for pdf_geometric etc, explicitly stating the definition. Closing this report as fixed. Thanks for the bug report, I appreciate your help.