Re: PERT distribution/risk

Dag Andersen wrote:
> Hi, need some guidance on this.
> 
> I find the following in the requirement spec:
> <quote>
> Durations are calculated for a task based on the resources assigned to 
> it. The following factors need to be taken into account:
> The effort required from each resource
> The risk associated with the resource/task pairing
> The availability schedule of each resource
> The other task commitments of resources
> 
> Note  [Jim Sabatke]
>   Allow task durations to be calculated from the following columns:
>  
>          "Optimistic Hours"    
>          "Pessimistic Hours"  
>          "Expected Hours"   
>          "Risk"    
>          "Duration"
>  
>          The "Duration" would be calculated like:
>  
>          "Risk" = Low        Duration = (OH + 4EH +PH) / 6
>          "Risk" = High      Duration = (OH + 4EH + 2PH) / 7
>          "Risk" = None      OH = EH = PH = "Duration"  
>  
>          If Duration is entered, then OH, PH, EH all will be set to 
>  "Duration" and "Risk = None"
> </quote>
> 
> It's the Risk that makes me uncertain. AFAICS it's a way to handle the 
> fact that some people are created more equal than others and hence, 
> that the time it takes to complete a task is dependent on the 
> specific resource(s) assigned to do the work.
> 
> Selecting a "High" risk thus effectively says: I don't think the 
> people assigned to this task is able to finish it within the normal 
> estimate, so I increase the estimate.
> 
> Also I think the risk must be interpreted to be for "resources 
> (plural)/task pairing" and not for "resource/task pairing" as stated 
> above? (Maybe what was meant anyway?)
> 
> IMHO it's not the estimate that should be modified but the efficiency 
> of the resource. To register this may be sensitive, though, and might 
> even be illegal in certain countries?
> 

Oh, one more thing.  High risk is not necessarily a reflection of the 
resources abilities.  It could involve many other considerations, like:

- suspected inadequate design because of client uncertainty (client 
expectations)
- suspected inadequate design because of client lack of experience 
(client expectations)
- new technology to either the resources or the company
- new, unproven versions of software
- and etc.

Jim