Lynda Bourne has a post at the PMI Voices of Project Management around Unrealistic Detail. I'm always puzzled when the conversation starts with "doing unrealistic things, and then expecting anything other than disappointing results."
This is the classic "doctor, doctor, it hurst when I do this," paradigm.
The second statement that piqued my interest was It's impossible to accurately predict the future. Yet, many project managers continue to try. This of course is both not true, and follows the quote above.
Of course you can predict the future it's done all the time, every day. From predicting the arrival of the school bus, to predicting the completion of a project and the cost of that project. What Lynda fails to include in the sentence of the probability that the prediction is accurate to some level of confidence.
The conversation goes like this There is an 80% probability of completing on of before the 3rd week of November, 2014 with a 7% error band. Or there is an 80% probability of the program costing $320M of less, with a 6% error band.
The probabilistic forecasting of cost and schedule is the core process applied to most of the program we work. It is mandated by DID 81650 and well most agencies procurement processes.
The fact that many project managers try to predict in the absence of probabilistic models is of course nonsense. Of course Lynda's statement...
They create schedules that implicitly state a task will be completed at 3:30 on a Tuesday afternoon, in four months. Or they predict that the total cost of their project will be precisely $10,986,547.55.
This is course nonsense, if there is no confidence interval and error band on that confidence. So Lynda is correct and at the same time completely wrong.
The PM might say, "Doctor, doctor, I try to make predictions with no confidence intervals and no error bands and I keep being disappointed in the result." The Doctor would tell you "Well stop doing that, and read to guidance for probabilistic forecasting in deterministic schedule and cost models."
It's really that simple. And like one of my favorite banners at Rocky Flats
Don't do stupid things on purpose