(01-11-2014 01:37 PM)Sanjeev Visvanatha Wrote: Hello,

I was comparing output between HP48sx MATHLIB [Ref. 1] and WP-34S (v 3.2 3375) for some of the probability distributions. For this purpose, I was replicating the examples from the HP-21S user's manual (pg. 42-52)

I noticed that the Inverse of the Chi-Square distribution for the WP-34S does not seem (to me) to produce the same result as what is listed in the 21S manual pg. 50.

Degrees of freedom = 19

Upper tail probability = 0.001

Keystrokes on WP-34S:

19 [STO] J

0.001 [h] [PROB] [ϰ²INV]

This results in 5.4068 (in FIX4)

The 21S example on pg. 50 of its user manual gives a result of 43.8202 (function name is ϰ²p). This is also consistent with HP-48sx MATHLIB function IUTPC(19, 0.001).

For reference, the IOP for the v3.2 manual of the WP-34S indicates that ϰ²INV should be equal to ϰ²p of the 21S. Is my understanding of how to use this distribution on the WP-34S incorrect?

Thank you for any insights you may have!

[1] HP 48SX Engineering Mathematics Library, John F. Holland

5.4068 is correct for 0.1%, while 43.8202 is correct for 99.9%

Integrating form zero to p, the value returned must increase for growing p (see pp. 54f of the manual quoted). The HP-21S calculates with the error probability instead.

d:-)