A recent twitter post started out with I predict my train will depart from platform 12 in 10 minutes: degree of predictability correlates with length of time I then asked and what is the evidence on which you base this estimated time of departure? I got back I didn't estimate departure, there is a timetable there, but Trains someone's run late & platform sometimes changes.
But in fact - mathematical fact - there was an estimate made. The trains are sometimes late informs the probability of leaving as planned
With the time table there is a target departure time, but unless you're riding the S-Ban from our Eching office to downtown Munich office, as I did for a year - the train departure is approximate. The S-Ban departure was "exactly" 8:04, first because it was Germany 1986, and second because the train was parked at the end of the line.
But no matter if the train is departing Eching station or a London station, or the Station in Lower Downtown Denver, "margin" is needed for both you the traveler and the train. This "margin" protects the Aleatory uncertainties that exist in ALL systems, even trivial systems. The airlines bake this into their schedules. I fly a lot. Many times we arrive early to no gate and have to wait. Rarely in good weather do we arrive late.
When we do arive late on Southwest Airlines, it's most always due to some Event based uncertainty. These are Epistemic uncertainties.
Both Aleatory and Epistemic uncertainties exist on projects and in real life. They are part of life all life.
Aleatory uncertainty is handled by margin. Epistemic uncertainty is handled with by down processes. Here's the details on managing in the presence of uncertainty. Uncertainties that are ALWAYS present. Uncertainties that ALWAYS require making an estimate of the probability of occurrence (Epistemic), range of variance (Aleatory), and probability of outcomes, and probability of the impact from those outcomes, and the probability of the residual uncertainty and associated risk when the initiating uncertainty is not 100% removed.
In other word, you can't make a decision in the presence of uncertainty without estimating all those variables - occurrence, outcome, impact, residual uncertainty. That's the way life - and projects work. Saying decisions can be made without estimating - #Noestimates - doesn't change the way nature and projects work, no matter how many times it is said. Especially how many times it is said without evidence of how to actually make those decisions without estimates.
