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MathGroup Archive 2002

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More weird integration issues...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35728] More weird integration issues...
  • From: "Binesh Bannerjee" <binesh at hex21.com>
  • Date: Sat, 27 Jul 2002 06:43:45 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi. I'm trying to compute the 5th moment of a tweak to the normal pdf.
Here's what I have:

F[a_, b_, c_, d_, e_, f_, X_] := (a + b X + c X^2 + d X^3 + e X^4 + f X^5)*
    Exp[-(((X - m)/sd)^2)/2]/(Sqrt[2Pi]sd)

The strange thing, and I'd appreciate someone shedding some light on this,
is that this:

\!\(Integrate[
    F[p\_0, p\_1, p\_2, p\_3, p\_4, p\_5, 
        X]*\((\((X - m)\)/sd)\)^5, {X, \(-Infinity\), Infinity}, 
    Assumptions -> {sd > 0}]\)

(I cut and pasted that it looks like it works)

Anyway, THAT gives me an answer really quickly... (within 5 minutes on my box)

JUST changing it from p0..5 to a,b,c,d,e,f like so:

Integrate[F[a, b, c, d, e, f, X]*((X - m)/sd)^5, {X, -Infinity, Infinity}, 
  Assumptions -> {sd > 0}]

Causes mathematica to go into an infinite loop (seemingly after 6 hours).

This ... sucks. How am I to know if a certain equation is solvable, if
only I choose the right variables??

Binesh Bannerjee

--
"For in much wisdom is much grief, and he that increaseth knowledge
 increaseth sorrow." -- Ecclesiastes 1:18

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