Point Lookout: a free weekly publication of Chaco Canyon Consulting
Volume 19, Issue 39;   September 25, 2019: Planning Disappointments

# Planning Disappointments

When we plan projects, we make estimates of total costs and expected delivery dates. Often these estimates are so wrong — in the wrong direction — that we might as well be planning disappointments. Why is this?

When people estimate how long a piece of work will take — or how much it will cost — their estimates are fairly reliable if they've done lots of similar work before. But if the work is unfamiliar, or if there are significant unknowns associated with the work, estimates of cost and schedule tend to be far less accurate, even when all we asked for was a "rough estimate." And the inaccuracies are almost always of a certain kind: final costs tend to exceed estimates, and deliveries are often late.

Why does this happen?

Last time, I explored three important contributors to this pattern — the planning fallacy, self-serving bias, and organizational politics. But in addition to these sources of systematic errors, there are two conceptual errors that are a bit mathematical in nature. One is a general misunderstanding of the term "rough estimate," and the second is a misconception about the shape of probability distributions of costs and schedules for unfamiliar projects.

Misunderstanding the term "rough estimate"
Rough estimates can be useful if we understand the true meaning of "rough." Technically, a rough estimate is an estimate that has a relatively wide margin of error. Every estimated value has a band of values that corresponds to, say, 95% confidence, and a mean or average that corresponds to a point within that band. If the width of the 95% confidence band is W, and the mean is M, then there is a ratio R equal to W/M. The "rougher" the estimate is, the greater is R.
To be safe, users of rough estimates need to use the value at the top end of the band for estimated values in which larger is worse, or the value at the low end of the band for estimated values in which smaller is worse. Too often, people just use M. They can be forgiven, of course, when the estimator provides M alone, without reference to a 95% confidence band.
There are clear reasons for this. In my experience, many consumers of estimates — the decision makers, as they're often called — are uncomfortable with any estimate that includes an uncertainty band. I've actually heard reports about decision makers' responses to estimates of the form, say, 8.7 million +/- 1.5 million, that go like this: "Don't give me this +/- stuff! If you don't know how much it will cost, just admit it! Now give me an estimate! Exactly what will this cost?"
In fairness, Rough estimates can be useful
if we understand the true
meaning of "rough"
many estimators lack sufficient information needed to compute a 95% confidence band. Others aren't sure how to calculate it. Others are intimidated by decision makers who reject the "+/- stuff," and still others aren't intimidated, but just don't want to fight with resistant decision makers. Whatever the case, estimates without 95% confidence bands are common, and because the estimates lack these bands, overruns are defined as "less favorable than the so-called estimate," which makes overruns very likely.
The shape of probability distributions of costs and schedules
Another source of estimation error is our human intuition about the shape of the probability distributions of costs and schedules. We tend to think of these distributions as fairly symmetrical around some average, or mean. And we also like to believe that the mean of, say, the cost distribution, is fairly close to the most likely value of that distribution.
We base this intuition on our experience with familiar efforts. And as it happens, for familiar efforts, our experience is a useful guide. That is, the distribution of cost or schedule outcomes for familiar efforts is fairly symmetric around some average value.
But for unfamiliar efforts, our intuition is misleading — sometimes grossly misleading. And this comes about for reasons that are easy to understand intellectually, but difficult to incorporate into our intuition.
With unfamiliar efforts, or efforts that are subject to significant unknowns, the probability distributions for costs and schedules aren't symmetric about their means. In fact, they're wildly asymmetric. While there are some pretty hard limits on how quickly or cheaply things can happen, there are no analogous limits on how slowly or expensively things can happen. For example, no matter how hard you try, you probably cannot get to the conference room in the other building in less than 45 seconds — even if you run. But without trying to dawdle, it can sometimes take you 20 minutes to get there, even though it's only a five-minute walk, depending on the weather, who you run into on the way over, and whether or not you have to go back to pick up something you forgot.
For unfamiliar projects, or projects subject to significant unknowns, the probability distributions for costs and schedules tend to have long "tails" corresponding to unanticipated costs and delays. These tails cause the distributions to have average values that can be much greater than their most likely values. And that's what throws off our intuitions. When we estimate, we tend to estimate the most likely value. And when the average value is much greater than the most likely value, our estimates tend to fall crazily short. The situation is even worse when we stack one task or project after another in a long train, because the uncertainty bands stack up.

Next time you make or receive an estimate without a 95% confidence band, ask yourself, "What are the lowest and highest values that wouldn't shock me totally senseless beyond all reason?" That should give you some idea of what 95% confidence means.

Projects never go quite as planned. We expect that, but we don't expect disaster. How can we get better at spotting disaster when there's still time to prevent it? How to Spot a Troubled Project Before the Trouble Starts is filled with tips for executives, senior managers, managers of project managers, and sponsors of projects in project-oriented organizations. It helps readers learn the subtle cues that indicate that a project is at risk for wreckage in time to do something about it. It's an ebook, but it's about 15% larger than "Who Moved My Cheese?" Just . Order Now! .

Thank you for reading this article. I hope you enjoyed it and found it useful, and that you'll consider recommending it to a friend.

This article in its entirety was written by a human being. No machine intelligence was involved in any way.

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## Related articles

More articles on Project Management:

Nine Project Management Fallacies: II
Some of what we "know" about managing projects just isn't so. Identifying the fallacies of project management reduces risk and enhances your ability to complete projects successfully.
The Politics of Lessons Learned
Many organizations gather lessons learned — or at least, they believe they do. Mastering the political subtleties of lessons learned efforts enhances results.
Risk Management Risk: I
Risk Management Risk is the risk that a particular risk management plan is deficient. It's often overlooked, and therefore often unmitigated. We can reduce this risk by applying some simple procedures.
Durable Agreements
People at work often make agreements in which they commit to cooperate — to share resources, to assist each other, or not to harm each other. Some agreements work. Some don't. What makes agreements durable?
Power Distance and Risk
Managing or responding to project risks is much easier when team culture encourages people to report problems and to question any plans they have reason to doubt. Here are five examples that show how such encouragement helps to manage risk.

## Forthcoming issues of Point Lookout

Coming September 4: Beating the Layoffs: I
If you work in an organization likely to conduct layoffs soon, keep in mind that exiting voluntarily before the layoffs can carry significant advantages. Here are some that relate to self-esteem, financial anxiety, and future employment. Available here and by RSS on September 4.
And on September 11: Beating the Layoffs: II
If you work in an organization likely to conduct layoffs soon, keep in mind that exiting voluntarily can carry advantages. Here are some advantages that relate to collegial relationships, future interviews, health, and severance packages. Available here and by RSS on September 11.

## Coaching services

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