Don't Write an SOP Like it's a Science Paper or a Regulation

I love working with scientists. But it's sometimes hard to teach them to write a good SOP! Why? Because they have the ‘scientific paper’ style of writing hammered into them. I'd get drafts filled with descriptive, information-dense paragraphs in the passive voice. Procedures written in the past tense. Citations everywhere. And I don't blame them at all - this was how I was taught to write as well, and decades later I'm still battling against the tendency to turn everything into a paper.
Contrast to when I started working with production facilities. Many of the people I needed to get procedures out of had no writing background at all, let alone any technical writing. However I found that it was easy to get good, clear, bullet-form descriptions out of them once they realised not to worry too much about the perceived quality of their writing.
In what seems to have become "SOP November", I have spent some time leaving the concept of the SOP rather open to interpretation. Today we’re going to narrow things down a bit and disavow several styles of writing that often shows up in SOPs. A warning for the faint-of-heart - I might get a little opinionated here!
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An SOP is
a Report or an Article.

Despite the simplicity of weighing, considerable complications are encountered in the determination of the uncertainty of measurement, as shown by Reichmuth et al. (1). Most standard operating procedures (SOPs) and guidelines for weighing with the aid of electronic-analytical balances (EABs) contain instructions on how to correct for various factors that may influence the determination of mass (2–5). Correction measures are believed to explain the difference between the mass of a given sample and its true mass. The determination of masses by EABs is influenced by numerous factors, including the tilt of the EAB, vibrations, eccentric load (1, 6), static electricity (7), magnetism (5, 8), electrical interferences (5), air flow (5), differences in gravitational force (1, 4, 9), buoyancy (1, 8–10), temperature, air pressure, density, and relative air humidity.
Reports and articles are there to communicate ideas and results to an audience. To do this, a good report might need to lay background, provide evidence and justification, discuss results, provide conclusions, and generally engage the audience in a way that builds and cements those ideas. However, as anyone who's tried to reproduce the results of a scientific paper would attest, these virtues do not lend themselves well as a
On the other hand, an SOP doesn’t need to do any of this. An SOP needs to tell its audience how to perform a task in a manner that is easy follow, meets any compliance requirements, and will be reproducible (at least in the ways that are important) across
. Things like background information, justification for how things are done and discussion don’t always lend themselves to the goal of an SOP, and in fact often clutter the document.

An SOP is
a regulation

(3) The cannabis referred to in paragraph (1)(d) is exempt from the application of subsection 2(4) of the Act and a quantity referred to in column 2 of the table to section 21 in respect of any class of cannabis referred to in column 1 is deemed to be equivalent to 1 kg of dried cannabis.
Because those of us writing and reviewing SOPs tend to be really close to the regulations, sometimes we mimic that style. So you see alot of
"§ All weights and measures MUST be within 5% of..."
But it's worth noting that most regulations are
at instructing people how to do something! Regulations are a bit like a hedge maze - big walls that stop you from going in any old direction that you choose, but otherwise do not help you get to where you want to go.
Regulations are written to a very broad audience, covering many possible cases, branches, and loopholes. Consequently, they tend to be very complicated, and sometimes become a spaghetti mess of cross-references, as my unfortunately very real world example above illustrates.
These are definitely not documents that are meant to be opened up and followed by someone. That's fine for the regulators - being comprehensive and able to exactly cite a clause is much more important to them than anyone being able to follow it on the fly.
While an SOP will often need to lay out rules, requirements and limits, think of them as part of the information used by the procedure rather than the procedures themselves. So any "Must" or "Shall" statements should be accompanied by some

An SOP is
a Training Manual.

A balance is a piece of equipment used for measuring mass. There are three kinds of balances that you might encounter at Happyco: animal, micro and analytical. You can tell which is an animal balance by the yellow panda sticker on them. Animal balances are special because they have an averaging function to counteract movement...
– Completely made up. Brendan, 2022.
Perhaps this is the one that made you stop and blink. Yes, we train people on SOPs all the time, but that doesn’t mean we should be writing all our SOPs for the
new guy who's never done it before
No. SOPs should be written
for the person who is using it day-to-day
. What’s the difference? Well, for one, you can assume that the operator has been trained on the procedure, knows the equipment, and has the required education and experience for the task at hand.
That way you can pick and choose how much detail needs to be written based on meeting quality and compliance requirements rather than having to thoroughly explain all the nitty gritty. Focus on the important details rather than getting lost in detail.
For example, an SOP could tell the operator when and how to perform a check weight and when to tare the balance without having to explain the concept of bracket weighings, what "tare the balance" means, how it differs from zeroing, etc. etc.
Maybe this is important information that all users of a balance should probably know… Great. Why not put it in a training document?

So how should a good SOP be written?

Be clear about the SOP's audience, scope and purpose. Then stick to it.
Favour direct, imperative statements for procedures.
Aim for a linear procedure that is complete for the given scope and purpose.
Be specific, but not too specific.
Provide visual cues to aid understanding.
Look for opportunities to guide quality and front-load effort.
Don't clutter the SOP.
Above all an SOP needs to be clear and direct, and the less distraction from its purpose the better. The best instructions are imperative, reserving declarative statements for setting requirements and describing outcomes.
While performing the procedure, the experienced operator should be able to find where they are at a glance and determine what the next step is quickly and precisely.
There needs to be a good balance in detail. Enough detail to ensure it's done the same way each time, meeting all your requirements. Little should be left to interpretation where compliance and quality are concerned. However, you don't want to be so detailed that the operators are losing the important parts of the procedure, or worse generating deviations (i.e. not following the SOP
as written) for things that don't really matter.
Finally, rather than "teaching" the operators, the SOP should have things that make the operator's job easier - quick reference tables and figures, pre-calculated values, maybe a troubleshooting section.
That's not to say that the teaching material isn't valuable - rather than cluttering the SOP with details that they won't be using every day, support the procedure (or set of procedures) with good training materials and a specification. When I'm working on an SOP, I often have a second document open where I can retain things that I don't want cluttering the SOP but would still be useful to have for training.
Until next time, thanks for reading!
– Brendan

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