March 3, 2008 – Estimating Lessons Learned – Side Track

After last week’s blog entitled “Estimating Lessons Learned” I received the following comment:

“On the contrary-publishing an estimate of 1,433 hours may be entirely appropriate, unless there's a general disclaimer and/or policy noting that all estimated in a named range are rounded up to the "developer day" (five or six hours) or to a calendar week.

Generally I avoid spontaneous schedule adjustments-over time, they'll distort the schedule and play havoc with historical analysis of estimating accuracy. Any moderately quantitative sponsor or executive stakeholder should question estimates that always end in "0", because it signals subjectivity in the estimating process, and that's something we don't want.” – posted by "badge number ?"

I don’t have time to write a full blog this week (finalizing a presentation for PSQT’s Las Vegas conference), but I do want to respond to this line of thinking.

Let me begin with the last statement: “...because it signals subjectivity in the estimating process.” If you work in an industry that is able to do quantitative analysis and produce a spot on estimate, go for it. The construction industry has a well established, quantitative estimating practice based on years of historical data. However, by definition (http://www.dictionary.com/) an estimate is “to form an approximate judgment or opinion regarding the worth, amount, size, weight, etc., of; calculate approximately.” The use of the words “approximate” and “opinion” denotes subjectivity.

Having said that let me agree with the reader’s comment on two counts. First, “publishing an estimate of 1,433 may be entirely appropriate.” It certainly is when you are putting together a Definitive Estimate. It is not true for a rough estimate when you lack the necessary information to be that accurate. If you can support the detailed estimate, give it to them. Otherwise, don’t give them a number that they will assume is more accurate than it is.

Second, “avoid spontaneous schedule adjustments.” They are bad. I have never advocated them and didn’t in my entry. There are key points throughout your project that you will have significantly more information. At these junctures it is important to re-evaluate the reality of your estimates and communicate any changes to management.

As we will see over the next couple of weeks, that communication begins by clearly stating the logic behind the original estimate with the estimating assumptions made to get there. When re-working the estimate later in the project, those assumptions are may not be true any longer. If the basis for your estimate changed you have a responsibility to communicate the resulting change in your estimate to management.