Concept: The To-Complete Schedule Performance Index (TSPI) is the starting point for assessing recoverability. Once the TSPI hits 1.1, the project becomes unrecoverable.
Don’t wait to breach that threshold. Instead, take action before it’s too late. How soon?
That depends on the “window” available for recovery. Walt Lipke has quantified the periods available for recovery, and the schedule efficiency required in each period.
We can intuitively assess whether the required efficiencies are achievable within the window, but the math goes beyond that.
It quantifies the probability of recovery.
Practice: Similar to other recovery metrics, practice with Probability of Recovery does not hinge on understanding the underlying math. Rather than start with the math, let’s start with its implementation. The math will come later.
Decision Dilemma
The case used in previous Recovery posts provides the background.
Say that part way through a 10-month project, the Schedule Performance Index for time looks like this:
The project got off to a slow start, but performance improved significantly. The SPIt is currently well above 90%, and it’s still climbing! That looks pretty good. It certainly doesn’t cry out for recovery.
How does the Estimate at Complete for time look?
Given that the Planned Duration is 10 months, the estimates are not too bad. The variance is converging, and the nominal amount is just slightly above plan.
Maybe, the project is not in trouble, and there’s no reason to initiate recovery.
What does the To Complete Schedule Performance Index tell us?
The late start and its nil SPIt throw off the first measurement. The other measurements seem to be hovering below the 1.1 threshold. Again, there’s no clear signal to start recovery.
So, what do you do?
Get more information.
The Window of Opportunity helps.
Based on performance to the end of June, the window is .132. That’s a narrow window—so narrow, that it would be reasonable to initiate recovery.
Still, recovery is a dramatic step, and a window remains open. Maybe, there’s other information to help us decide.
One such piece of information is how the recovery needs to proceed. With that, we can assess whether future efficiencies are realistic.
The Improvement Profile gives us the data. It looks like this.
As the graph makes clear, the efficiency improvements are striking. Almost all of them exceed the maximum efficiency attained thus far.
Furthermore, after a sharp initial increase, efficiency improvement has slowed. The SPIt has been well below the level required of future efficiencies.
That’s more evidence to start recovery.
And, yet, it might be argued that the future recovery rate appears to be lower than the rate achieved through the first three periods.
(Mathematically, the initial rate is “N/A” because it starts from 0. The slope of the first curve, however, suggests that the project is capable of improving efficiency very quickly.)
It’s a thin thread, but there’s reason to hold the decision in abeyance.
Picking up the thread, suppose another month has elapsed, and it’s now the end of July. Efficiency remains essentially unchanged at .958. Consequently, the SPIt and EACt remain much the same and are not shown.
With the shortening of available schedule, however, the TSPI and Window of Opportunity are significantly altered. TSPI rises to 1.097, just slightly below the threshold. The Window of Opportunity shrinks to .006, just slightly open.
Strictly speaking, neither measurement breaks a threshold value and so are not shown. Recovery is still possible, although intuitively is seems unlikely.
A final recovery metric decides the issue.
The probability of successful recovery peaks in April. Then, from April through June, the decline in probability is unremittent. That’s bad enough, but in July it gets worse.
The decline not only continues; it reaches 50.82. And, that’s a threshold.
At 50%, successful recovery becomes a matter of chance. Recovery must depend on more than a roll of the dice. It demands action, and so, delay is no longer an option. It’s time to recover the project.
PS Starting recovery a month earlier would have been appropriate. At that point, there were already three periods in which the window of opportunity narrowed, requisite efficiencies climbed, and probability of success dropped. The trends make it reasonable to take action without waiting to hit the threshold. |
