Fantasies are as ethereal as a cloud.

Fantasies are as ethereal as a cloud.

There are a number of fantasies about estimation that non-IT people and even some experienced software development professionals have. They are that 1) estimates are like retail prices, a predictable fixed price, 2) estimates can always be negotiated to a smaller number with impunity, and 3) in order to be accurate estimates must be precise. The belief in any of these fantasy fallacies will have negative.

The first fantasy is that is that custom projects can be priced like a cup of coffee. We fall prey to these fantasies because we are human and we want software projects to be as predictable as buying that cup of coffee.  When you go to most coffee shops, whether in North America, South America, Europe or India to buy a cup of coffee, the price is posted above the register.  In my local Starbucks I can get a cup of coffee for a few dollars, I just read the menu and pay the amount. The same is true for buying an app on my iPhone or a software package. Software project estimates are built on imperfect information that ranges from partial requirements to evolving technologies and, worse yet, include the interaction of people and the chaos that portends.  From a purely mathematical perspective these imperfections mean that the actual effort, cost and duration of the project will be variable.  How variable is influenced by the process used, the amount of learning that is required to deliver the project and the number of people involved. These are just a few critical factors that drive project performance. This variability in knowledge is why mature estimation organizations almost always express an estimate either as a range or as a probability, and why some organizations suggest that estimation is impossible. Agile projects re-estimate every sprint based on the feedback from the previous sprint using the concept of velocity.  Many waterfall projects re-estimate at the beginning of every new phase so that the current estimate utilizes the information the team has learned through experience.  Even when a fixed price is offered, the organization agreeing to a fixed price will have done an analysis to determine whether they can deliver for that price and what the probability is that the project will really cost (with a profit). This would be the process followed for any project to say they were x% confident of an estimate. When projects run short on time, resources or money and they can’t beg for more, they will begin to make compromises ranging from cutting corners (we don’t need to test that) to jettisoning scope (lets push that feature to phase two).  Many of these decisions will be made quickly and without enough thought, which will hurt IT’s reputation and increase project risk.

A second classic fantasy is that you can always brow beat the team into making the estimate smaller.  This fantasy can be true.  A good negotiator will leverage at least two physiological traits to whittle away at an estimate.  The first trait is the natural optimism of IT personnel, which we discussed in Software Project Estimation: Types of Estimates.  The problem is that negotiating the estimate downward (rather than negotiating over scope or resources) can lead to padding of estimates or to technical debt driven by pressure on profit margin or on career prospects. Estimators that know they are going to be pushed to reduce any estimate regardless of how well it is built will sometimes cheat and pad the estimate. So, when they are pushed to cut they can do so without hurting the project. This behavior is only a short term fix.  Sooner or later (and usually sooner) sponsors and managers figure out the tactic (perhaps because they used it themselves) and begin demanding even deeper cuts.  The classic estimation joke is that every first estimate should be cut in half and then sent back to be re-estimated.  A second side effect of this fantasy is that when the estimate is compressed and the requirements are not reduced, the probability of the team needing to cut corners increases.  Cutting corners can result in technical debt or just plan mistakes.  In extreme circumstances, teams will take big gambles on solutions in an attempt to be on budget.

A third fantasy is that precision equals accuracy. Precision is defined as exactness.  A precise estimate for a project might be that a project will cost $28,944 USD and require 432 hours, will take 43 days beginning January 1st and completing February 12th. Whether the estimate is accurate, defined as close to actual performance, is unknown.  This is precision bias, a form of cogitative bias, in which precision and accuracy are conflated.  In most cases in precision bias occurs the high precision infers higher accuracy.  The level of precision gives the impression that it is highly accurate.  The probability of a highly precise estimate being accurate is nearly zero, however add few decimal places and see how much more easily it is to be believed. As we have noted before, wrong budgets and/or estimates will increase the risk of project failure.

When I teach estimation I usually begin with the statement that all estimates are wrong.  This is done for theatrical effect, however it is perfectly true.  Any estimate that is a single, precise number that has gone through several negotiations (read that as revised down) is nearly always wrong. However, if when we jettison the false veneer of precision, integrate uncertainty and stop randomly padding estimates, we can construct a much more accurate prediction of how a project will perform.  Always remember that an estimate is a prediction, not a price.

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