Re: st: RE: Calculating binomial probability distribution of cumulative outcomes of independent events with differing values and probabilites

[Wally Knox <wallyknox@earthlink.net>]

Thanks for the comment, Martin.  I'm at a loss as to why my machine is  
objecting to the forvalues command.


Wally


On Jan 11, 2009, at 3:43 PM, Martin Weiss wrote:

> My machine does not complain about the -forvalues- thing (which is  
> correct, no doubt) but does not like the combination of a "*" with  
> the three slashes. It is only when I remove those and put the  
> separated commands on one line that Maarten`s code actually does  
> something.
>
> HTH
> Martin
> _______________________
> ----- Original Message ----- From: "Wally Knox" <wallyknox@earthlink.net 
> >
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Monday, January 12, 2009 12:18 AM
> Subject: Re: st: RE: Calculating binomial probability distribution  
> of cumulative outcomes of independent events with differing values  
> and probabilites
>
>
> > Maarten,
> >
> > Thanks for your reply.  I'm unfamiliar with matrix commands but  
> > will learn.  I tried running your do-file and got the
> > response "unrecognized command:     forvalues invalid command name" .
> >
> > I agree and understand that I am just using Stata as a glorified  
> > calculator, but that is fine with me.
> >
> > Wally
> >
> > On Jan 11, 2009, at 11:06 AM, Maarten buis wrote:
> >
> > > --- Wally Knox <wallyknox@earthlink.net> wrote:
> > > > I would like to calculate the probability distribution of the
> > > > cumulative outcomes of independent events each of which has
> > > > a different value and a different probability.  For instance, take
> > > > three events.  Event One has a probability of .9 and would
> > > > contribute 12 to the overall outcome.  Event Two has a probability
> > > > of .5 and would contribute 2 to the overall outcome.  Event Three
> > > > has a probability of .2 and would contribute 6 to the overall
> > > > outcome.
> > > <snip>
> > > > I am told that to obtain the likely outcome of the events to  
> > > > multiply
> > > > their individual probabilities by their individual values and sum  
> > > > the
> > > > results.
> > >
> > > The probability distribution will give you the probability of each
> > > possible outcome, so in that case you need to multiply the
> > > probabilities and not the probabilities with the outcomes. The
> > > computation someone else told you to do will not give you the
> > > probability distribution but the expected value.
> > >
> > > There is thus no need to use Stata for computing this probability
> > > distribution, but you can us Stata as a calculator. In the example
> > > below I use the fact that Stata sees the value 0 as false and 1 as
> > > true, for more on this trick see:
> > > http://www.stata.com/support/faqs/data/trueorfalse.html .
> > >
> > > *--------------------- begin example --------------
> > > matrix res = J(8,5,.)
> > > matrix colnames res = event_1 event_2 event3 Prob y
> > > local i = 1
> > > forvalues e1 = 0/1 {
> > >   forvalues e2 = 0/1 {
> > >       forvalues e3 = 0/1 {
> > >           local p = cond(`e1', .9, .1) * ///
> > >                     cond(`e2', .5, .5) * ///
> > >                     cond(`e3', .2, .8)
> > >           local y = cond(`e1', 12, 0) +  ///
> > >                     cond(`e2', 2, 0)  +  ///
> > >                     cond(`e3', 6, 0)
> > >           matrix res[`i',1] =            ///
> > >                  `e1', `e2', `e3',       ///
> > >                  `p', `y'
> > >           local `i++' }
> > >   }
> > > }
> > > matrix list res
> > > *--------------------- end example ------------------
> > > (For more on how to use examples I sent to the Statalist, see
> > > http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )
> > >
> > > Hope this helps,
> > > Maarten
> > >
> > > -----------------------------------------
> > > Maarten L. Buis
> > > Department of Social Research Methodology
> > > Vrije Universiteit Amsterdam
> > > Boelelaan 1081
> > > 1081 HV Amsterdam
> > > The Netherlands
> > >
> > > visiting address:
> > > Buitenveldertselaan 3 (Metropolitan), room N515
> > >
> > > +31 20 5986715
> > >
> > > http://home.fsw.vu.nl/m.buis/
> > > -----------------------------------------
> > >
> > >
> > >
> > > *
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> > > *   http://www.stata.com/help.cgi?search
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> >
> > *
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>
>
> *
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*
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