ProjectFlightDeck

Concept: In theory, Schedule Adherence and Schedule Efficiency offer a balanced perspective on schedule performance. In practice, the balance is skewed, and that affects SA’s advantages and disadvantages as a performance metric.

Practice: Let’s start with the difference between Schedule Adherence and Schedule Efficiency. (The original post can be found here.)

Schedule Adherence measures the degree to which the sequence of actual value delivery aligns with the sequence of planned value delivery. By contrast, Schedule Efficiency measures the degree to which the volume of actual value delivery aligns with the volume of planned value delivery.

The difference between the two is analogous to the difference between the wheel alignment of a car and the fuel efficiency of the car.

Take fuel efficiency: it measures the miles you can travel on a certain amount of gas. The mileage tells you if you are where you should be given the fuel that has been burned. The actual mileage on a trip can be above, below, or at the rated fuel efficiency of your vehicle.

Wheel alignment behaves differently. For your car to run straight, the wheels must be properly aligned, but the wheels are either in alignment, or they are not. Although the wheels can be wildly out of line, they cannot be better-than-aligned. So, alignment must fall between two limits.

The way these measures are actually used affects SA as a schedule performance metric.

Pro:

Schedule Efficiency indicates whether or not the volume of delivery meets the plan, but it does not give the whole story. For instance, suppose that value missing from late deliveries is offset by value gained from early deliveries. The overall volume fits the plan, but surely something is amiss—the planned sequence is not being followed. (For an example of such a case, look at Figure 4 here.)

That’s where Schedule Adherence can come into play. For SA, it matters very much which deliverables are completed. It flags when deliverables are being done out of sequence and what deliverables are causing the deviation.

For a well-rounded picture of schedule performance, both the efficiency of execution and its adherence to the plan are required.

Con:

The main downside to SA is its unfamiliarity. To measure schedule performance, adherence is not as widely used as efficiency. If it were, metrics related to the sequence of delivery would be as commonplace as metrics for volume of delivery. But, there is an obvious shortage of adherence metrics.

The predominance of volumetric metrics colours the perception of schedule problems. For instance, delays induced by impeded/constrained tasks constitute variance from the planned sequence, and they are commonly measured. Such variance, however, is usually viewed as a problem in volume rather than sequence.

For work done ahead of time the situation is even worse. There, early delivery is viewed positively:  “Great! We’re ahead of schedule!” The fact that such work can incur rework is often ignored. So, it is rare for projects to track the occurrence of rework, let alone quantify the effect on cost and schedule.

Finally, popular methods espouse the view that planned networks of deliverables should neither be required nor desired. The Agile framework, for example, encourages “on-the-fly” selection of deliverables from Sprint to Sprint. [1] In canonical Agile projects, there is no stable sequence against which adherence can be assessed.

Let’s face it: SA’s grounding in principles and math aligns it with thinking that is conscious, effortful, and (comparatively) slow. That contrasts with thinking that is fast, instinctive, and unconscious—the default mode for thinking and the driving force behind intuition. It’s easier to grasp and use approaches that draw on the latter than it is the former.

So, it’s unsurprising that SA’s unfamiliarity remains a challenge to SA’s adoption.

Notes:

[1] Agile projects cannot guarantee that a fixed network of deliverables exists. The rule of Independence means that equivalent deliverables (aka, Backlog Items) can be substituted for one another. Thus, the order in which deliverables are executed is determined on-the-fly. For more on the rule of Independence, see the INVEST mnemonic (Wake, 2003). For more on my response, see Van De Velde (2019), p. 172.

References:

Lipke, W. (2012). Schedule Adherence and Rework. CrossTalk, November-December.

Lipke, W. (2011b) Schedule Adherence and Rework. PM World Today, July.

Lipke, W. (2011a) Schedule Adherence and Rework. The Measurable News, Issue 1 (corrected version).

Van De Velde, R. (2019). Act Fast and Think Fast: Agile Schedule Performance. In M. Phillips (Ed.), The Practitioner's Handbook of Project Performance: Agile, Waterfall and Beyond (pp. 170-190). London and New York: Routledge.

Wake, B. (2003, August 17). INVEST in good stories, and SMART tasks [Blog post].  Retrieved from http://xp123.com/articles/invest-in-good-stories-and-smart-tasks/.

Over the past months, I have focused my posts on Schedule Adherence (SA). I started by reviewing basic SA concepts from Walt Lipke’s research: P-Factor, Schedule Adherence Index, Rework, and cost of Rework. Along the way, I spelled out details behind Walt’s (sometimes) condensed math and offered explanations of technical terms such as “e”.

Then, I clarified SA by showing that R-tasks and I/C-tasks are mutually exclusive, proposing the Impediments/Constraints Index, and deriving I/C cost. To explain the practical import of I/C cost, I called on the notion of opportunity cost.

Finally, I anticipated objections to these points—the major one being that they conflict with intuition. As an antidote, I showed how to construe SA as a “principle-based formal framework”.

Throughout the posts, I have consistently tied theory to practice, explaining how the metrics can be used to manage schedule performance on projects.

Now, it’s just about time to introduce a new topic. But, first, to close my posts on SA, I will highlight the Pro’s and Con’s of using adherence for schedule performance management.

In presenting the Pro’s and Con’s, I will cite one Pro/Con pair at a time. Generally, the Pro and Con will be related to the same theme, but sometimes, the pairing will be random.