Post 2: Lag vs Lead

It was 4:20am.

Standing in a cold, fog laden vale in the middle of Staffordshire, mentally numbed by the circadian kicking that a night shift carries out, and physically numbed by the unseasonal damp, I consoled myself that this was the last ‘big push’.

I, along with a small number of hardy souls, were tasked with earthing freshly installed overhead power lines along a 20 mile stretch of railway, between Stafford and Crewe. This was a part of being a Project Engineer in the rail industry; sometimes – most times – you mucked in with everyone. It was the culmination of a job I’d been involved with for the past 12 months.

We’d worked out the rate of gantry completion per hour. We calculated how many drill bits we’d get through for each gantry (railway sleepers need to be resilient – they have an incredible amount of tonnage to handle on a daily basis). We even took into account the mild gradients we’d need to deal with when pushing our trolley (yes, one of these) along the line.

In the world of functional performance, the project had one lag measure – that the number of completed gantries was enough to safely switch on the power lines to serve the upgraded West Coast Main Line. However, there were numerous lead measures – all of the intricacies named above – gantries per hour, drill bits per gantry, gradient of line, etc.

The lag measure was the outcome – it was the result of our effort. The lead measures were everything that contributed to the outcome – elements that we had control over. Once you have a lag measure, there’s nothing you can do about it – the goal is achieved, or it isn’t.

Lead measures, however, are things you can do something about. If, in our earthing, we weren’t getting through the gantries at the right rate, then we could up the rate. If we were getting through too many drill bits, then we’d have to take things easier, or somehow get hold of some more. Either way, to improve performance in terms of lead measures, we’d have to increase three things:

  • The number of people on the task;
  • The amount of physical or mental resources available;
  • The amount of time available.

For far too long in UK education, we have focused too much on the lag measures – grades, marks, etc, as an arbiter of whether our efforts are good enough. But the problem is that lag measures tell you nothing other than if a goal has been achieved. What they don’t tell you is the story behind the outcome and if, in the myriad of variables and noise that we have to manage on a hourly, daily, weekly and yearly basis, that the elements that contribute to the outcome were successful.

It’s the lead measures that give an indication (more on this choice of wording later) of if a successful outcome is going to be achieved. If you can identify the elements that have the greatest leverage over understanding of your subject, then you have lead measures for your teaching. If your lead measures indicate that you might not achieve your goal – then you can invest the aforementioned people, resources and time that are required.

There are challenges with lead measures:

  • You need evidence to show if your measures are truly lead measures! Unless you do a piece of work like William Emeny did with the GCSE Mathematics specification, then it takes a few years’ experience to piece this together.
  • If you’re responsible for creative arts subjects, then you’re often making objective statements about subjective qualities: how much does a students’ skill with their pencil actually indicate their artistic temprament?
  • How many lead measures, and to what level of detail, should one track? If you dissect your subject’s domain too far, are you not losing the essential qualities of your subject?

Equally challenging in teaching is the pure fact that there is still a ‘black box’ element to how our students will perform; for all the time, analysis and preparation that we carry out in service to our students, their physical and mental state is a significant contributor to how they translate many year’s effort into a single performance. GCSE results are our students’ Olympic Games; an athlete can still choke after 4 year’s conditioning for the event, and thus analogously even the most confident and well-prepared student can quake in the exam hall.

Hence why I use the word indicator in relation to lead measures in teaching – you cannot truly quantify a student’s mastery (and thus retention) of a concept, until the lag measure is obtained – and even then, much is down to performance on the day.

This shouldn’t dissuade from working on lead measures. Micro-scale investments of time and energy on multiple process elements earlier a project will have a greater net gain than the risk of big investments as a deadline looms – as I allude to here.

Postscript: As it happened, we got the earthing job done. We had to up the rate of effort a little and this required lifting the trolley onto the back of a pick-up truck and drive to the next access point to up the pace somewhat. We rushed the lifting, and the trolley slipped, crushing my right index finger. Ironically, by focusing on a lead measure, we completely re-set a significant lag measure for the whole project – one million man hours of accident-free work ruined, in the space of one night shift.


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