23 April 2012

Why Critical Path Scheduling (CPM) is Wildly Optimistic

Pat Weaver has a really well written paper about the fatal problems with CPM. He goes beyond the flaw of averages issues and covers the topic in depth.

I'm not sure I agree with all his prescriptions, but it does have me thinking about my preconceptions.

The abstract and link to download the pdf are here.

22 April 2012

Reading Sample Distributions

Usually, "How long will it take to do this?" doesn't have just one answer. Whether 'this' is a small task or a large project, it has a whole bunch of answers - each with its own probability of being right or nearly right. The answer is an uncertain variable; it's a variable because it can have more than one value and it's uncertain because we don't know what the variable's value is (or will be). We don't know how long it will take to finish the task and we won't know for sure until it's done. Until then, it's an uncertain variable. After that, we refer to it as an actual value.

Unfortunately, we can't leave it at that. There's a third value we call the plan value. That's the value we aim at, the value we hope will be right, the value we use to coordinate with other related activities. That's a value we choose and, hopefully, we make that choice knowing what the associated risks and probabilities are. Tagging along with that choice is the project schedule we hope will produce it, and the associated project cost we hope not to exceed. We don’t “manage” uncertainty; we stare it in the eye and make a decision.

14 April 2012

Cobb's Paradox

"We know why projects fail, we know how to prevent their failure -- so why do they still fail?" Martin Cobb, CIO, Treasury Board Secretariat, 1995

Seventeen years - and still no answer.

Actually, there is an answer, but the question seems to have become unpopular.