Project Management

Pay No Attention To The Earned Schedule (Straw) Man Behind The Curtain!

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When an author attempts to advance a theory under the auspices of Management Science using obvious sophistry, I immediately know two things:

  • The theory has not been proven, or even logically advanced past the hypothetical phase, and
  • Any practitioner of the legitimate hard sciences is fully justified in rolling their eyes clear to the back of their heads whenever they hear the term “Management Science.”

Of course, many instances of sophistry are difficult to detect, at least right away. Not so the case with the straw man argument, no siree. This is where the theoretical position opposite the assertion being advanced is set up, but not accurately, then criticized to oblivion. And this is exactly the tack being taken with much of the advancement of earned schedule (like “risk management,” I refuse to use initial caps for this term).

What is “earned schedule?” Well, from the self-proclaimed “official site for Earned Schedule,” we see this:

Earned Value Management (EVM) is a wonderful management system, integrating in a very intriguing way, cost …schedule …and technical performance. It is a system, however, that causes difficulty to those just being introduced to its concepts.  EVM measures schedule performance not in units of time, but rather in cost, i.e. dollars.  After overcoming this mental obstacle, we later discover another quirk of EVM: at the completion of a project which is behind schedule, Schedule Variance (SV) is equal to zero, and the Schedule Performance Index (SPI) equals unity.  We know the project completed late, yet the indicator values say the project has …perfect schedule performance!![i]

In just these five sentences we can begin to see the vacuousness of its underpinnings. Quick question: why does the author feel the need to refer to EVM as “wonderful” and “intriguing?” Also in the first sentence, the author doesn’t understand how to use ellipses, twice interjecting them for commas, and don’t get me started on multiple exclamation points. Does that last objection sound like nit-picking? Maybe so. I just have a hard time taking advice on how to better manage hundreds of thousands of dollars’ worth of projects (if not millions) from a person who hasn’t mastered eighth-grade English.

The third sentence points out that Earned Value Management (EVM) measures schedule performance in units of cost. Umm, yeah, that’s what EVM does. If you want to measure schedule performance in terms of time, which earned schedule claims to do, then the traditionalists would turn to – Critical Path! That’s what CPM does. In another document, generated by a certain guidance-document-generating organization that I refuse to name, the example given for earned schedule has to do with reducing plans to meet friends for dinner to PM terms. The story problem stipulates that, at your current rate of performance, you will be late to a dinner with friends, and goes on to mock the idea that you would contact them to announce that you will be X “dollars late.”

But this is a straw man argument, and, therefore, invalid. When an EVM system returns that one will be $X late, it doesn’t mean that time equals money (though some would argue the contrary). It simply means that, if you want to arrive on-time to your dinner date, you should be prepared to spend $X over and above what you had originally budgeted to make that happen. Variances at Completion expressed in units of time are not properly derived from an EVMS – again, they come from Critical Path Methodology systems. It is, in fact, their raison d’etre. And yet the earned schedule crowd seems to assert that this new technique has bridged some previously-unsolvable management information gap. It’s simply not so.

Another straw man argument from the excerpt above challenging EVM and its schedule performance metric has to do with the fact that the Schedule Performance Index (SPI, or the cumulative Earned Value amount divided by the time-phased budget), in a “quirk,” moves toward 1.00 as the project comes to completion, regardless of whether or not it is finishing on-time. Again, this is an irrelevant observation. The SPI simply measures progress against the baseline; of course it’s going to close in on 1.00 as the project nears completion. There’s no “quirk” about it. You want a performance measure that compares a projected finish date to the original baseline date? That comes from the CPM system, and for experts to blithely fail to take this into account is sophistry.

I understand that the concept of earned schedule has received a lot of attention and accolades in the PM world. So has risk management. So has communications management. I also understand that it only took a random Cairn Terrier to pull back the curtain on the Wizard of Oz.


[i] Retrieved from on April 25, 2021, 18:45 MDT.

Posted on: April 26, 2021 10:23 PM | Permalink

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