[kplato] definitions of effort and risk

[John D Lamb]

Thanks. I think I've also worked out what risk is:

Risk: a simple estimate of the shape of the distribution, given
optimistic, pessimistic and expected efforts.

This fits with my earlier thought that "risk" could be represented by a
Distribution superclass (at least from the "document" or
"implementation" point of view: "Risk" is probably better from the users
point of view). Zero risk would be a fixed value, low risk is probably
beta-shaped and high risk lognormalish. The precise shape of the
distribution would not be important. From the implementation point of
view, it might be useful to represent risk by some real distribution
that gave the same values for duration, but could also give random
values and confidence intervals if later we need them: i.e. "fit
E(p,o,e) to a curve and calculate the risk from that".

I would definitely try to define risk without using standard deviations.
Standard deviations are good for *measuring* uncertainty, but not
intuitive for most people when *specifying* uncertainty. Optimistic,
Pessimistic, expected and a "Risk" factor ought to work just fine.

We might have to use Monte-Carlo simulation for a "project confidence
interval". But I think it would be sensible to get an initial project
first.

JDL

Jim Sabatke wrote:
> 
> Actually, because E(p) is usually a good bit larger than E(o), the
> distribution is skewed.
> Also, come to think of it, we should be calculating a confidence value
> so that we can multiply them up the chain to obtain an ovall project
> confidence.
> 
> Jim
> 
> bilbo wrote:
> 
> >On 21 Jun 2001, at 20:15, Jim Sabatke wrote:
> >
> >>I guess the tabs didn't expand well for you.  Sorry.
> >>
> >
> >My problem, probably, but I try to avoid tabs :-)
> >
> >>Most PM software expects the user to enter either:
> >>
> >>1.    E(p), E(e) and E(o)
> >>2.    E(p), E(o) and a std. dev. value, which is way above most PM's
> >>(IMHO) to use correctly.
> >>
> >Isn't that assuming symmetrical distribution of E(p) and E(o)?
> >
> >>You are correct that the values would be entered based on experience.  I
> >>am actually trying to create something more intuitive to the average PM
> >>by adding a risk factor column.  The PM wouldn't need the math, just a
> >>comparative judgement call (high/low/normal risk).
> >>
> >
> >The sw person in me wants to try to fit E(p,o,e) to a curve and
> >calculate the risk from that. I don't think that's going to work.
> >
> >Thanks for explaining that.
> >regards,
> >        Bill