Talk:Program Evaluation and Review Technique
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[edit] Two of a kind
There are two kinds of PERT diagrams. One is the sort shown in the article, which has nodes denoting stages of the project and arrows denoting tasks. The other sort, which I did at college, has nodes denoting tasks and arrows denoting the dependencies between them. The nodes tend to be shown as boxes with task information in them - there are various formats, one of which is like this
| 14 | 3 | 17 |
| Do something | ||
|---|---|---|
| 19 | 5 | 22 |
where the boxes are
| early start | duration | early finish |
| Task description | ||
|---|---|---|
| late start | slack | late finish |
(I'm not sure if the "early finish" and "late start" boxes were this or the other way round.) -- Smjg 16:14, 31 Mar 2005 (UTC)
[edit] Lead time
I always thought that one of the major, long-term contributions of PERT for those estimating completion times for complex tasks involving the interaction of many different tasks of many different types from many different sources was the concept of lead time.
The Wiki-article Lead time makes no mention of PERT as the term's point of origin.
Also, it seems very puzzling to me that most are speaking of lead time as if it means "the time taken to produce some manufactured article"; where, according to how I always understood its meaning, application, and implication was that the "lead time" for a particular event was the amount of time before a specific point in time that one would have to commence the activities that would generate the event in question by that designated "point in time".
Thus, the "lead time" means something very significant, and something rather like "the time one commence activity in advance of an event in order for the event to occur at X point in time".
Therefore, it does not (and can not) mean what seems to to be an identical, polar-opposite meaning -- which is very different, entirely wrong, utterly misrepresenting, and totally bereft of the wonderful utility of the term's correct application -- that we see in much of the usages: i.e., something like "the earliest time in the future that an event can occur if we start now" (rather than the correct version, "the latest we can start work, so that we will have the product in our hands on date D at time T).
I feel that there should be:
- (a) some significant piece about "lead time" in the PERT article; and
- (b) once that is settled, appropriate changes also made to the Lead time article.
Although I may have my wires crossed, I have always thought that "lead time" was the amount of time that had to "lead" or come before the event (and that this was why it was used in the planning and setting up events and processes so that they would finish by a particular date, such as the opening ceremony of the Olympic Games); rather than it being the amount of time beyond this moment that we could expect a finished product to turn up. Can anyone clarify this for me? Lindsay658 04:22, 17 July 2006 (UTC)
- Dbsheajr. I hope that what I have added assists. Please feel free to alter it in any way that better suits what you are adding to the remainder. Best to you Lindsay658 05:08, 25 July 2006
