At a glance
- Professionals must communicate risk and uncertainty to their clients.
- To gain trust, you must first demonstrate your trustworthiness.
- Be open about uncertainty and admit that advice can change.
- Always state your level of confidence in your own analysis.
Most accountants need, at some point, to communicate ideas of uncertainty and risk. Businesses explore deals which they know might go sour. An unexpected event endangers an organisation’s reputation and revenue. Investors contemplate buying securities whose value might plunge.
We have plenty of ways to quantify these risks and uncertainties. But many people struggle to understand how they were assessed, what they mean and whether to trust them. How do professionals talk with their clients effectively about these issues?
One of the world’s most prominent statisticians has some ideas.
Sir David Spiegelhalter started as a mathematician – “a not very good mathematician”, he tells Financial Accountant – and moved slowly from mathematical statistics into applied statistics. It seems a well-judged transition: by 2007 he became Cambridge’s Winton Professor of the Public Understanding of Risk, a position he held for more than a decade. He now chairs Cambridge’s Winton Centre for Risk and Evidence Communication, as well as serving on the board of the UK Statistics Authority.
Earlier in his career, Spiegelhalter’s writings tended to have titles like “Bayesian Measures of Model Complexity and Fit”. These days, he works hard at explaining issues of risk and uncertainty to the general public. Hence his 2025 book, The Art of Uncertainty: How to Navigate Chance, Ignorance, Risk and Luck.
How to demonstrate trustworthiness
Spiegelhalter describes accounting as one of several professions which offers advice to decision-makers – “and we’ve got professional ways in which we’re supposed to do that”. All these professions, he notes, share a need to communicate with their clients information about risk and uncertainty.
And of course, all of these professionals need to be trusted.
Spiegelhalter’s contribution in The Art of Uncertainty has been to assemble the evidence for the idea that organisations seeking trust should aim to demonstrate trustworthiness. “Audiences may then choose to offer up their trust, and the organisations will deserve it”.
To do that in a world of uncertainty, Spiegelhalter turns to UK zoologist John Krebs. Krebs chaired the UK Food Standards Agency (FSA) between 2000 and 2005 the agency had to communicate about sensitive issues such as chemicals (in this case, dioxins) in milk. Krebs aimed to communicate five different things in such emergencies:
- what we know (knowledge)
- what we don’t know (uncertainty)
- what we are doing to find out (plans)
- what people can do in the meantime to be on the safe side (self-efficacy); and
- that advice will change (flexibility and provisionality).
Openness about uncertainty
Spiegelhalter emphasises points two and five in the list above, on uncertainty and provisionality. People, professionals included, are frequently loath to say “I don’t know”. Yet if you want to show trustworthiness, he says, “you’ve got to be upfront about uncertainty. You can’t pretend that things are known when they’re not known.”
In particular, Spiegelhalter argues that people speaking about evidence should spell out the quality of that evidence. “You might have massive databases [that make it] absolutely clear-cut what’s going on … But [at] other times you really think ‘wow, we’re in a new situation; things are very volatile’.” In such volatile and uncertain situations, he says, organisations may need to admit that the evidence for particular situations is weaker than they’d like.
Communicating uncertainty during COVID
Communications experts often worry about appearing uncertain. But Spiegelhalter argues that in inherently uncertain situations, appearing too certain is likely to land you in trouble. Krebs showed that in many situations experts will do better with a more frank and open approach.
The merits of the Krebs approach showed in the earliest stages of COVID, Spiegelhalter says. Initially, in March 2020, health authorities advised the wiping of surfaces. This, it soon became clear, was bad advice.
“You’ve got to be upfront about uncertainty. You can’t pretend that things are known when they’re not known.”
David Spiegelhalter
As Spiegelhalter recalls: “People were wiping surfaces a year later, when we knew within a month it is a complete waste of time … But the advice didn’t change, because they could say ‘oh, we can’t change our advice’.”
It later came to light that the government was anxious not to be seen as having made a u-turn. “So they have to carry on talking nonsense, because they never say that ‘what we’re advising will change as we learn more … COVID was an area of pretty deep uncertainty. That is a situation where you should not be giving advice as if this is the absolute truth.”
Politicians and other leaders failed to admit their advice was provisional and could change with new information. This bred deep distrust – the opposite of what they wanted.
The bottom line: expose your uncertainty
Nowadays, Spiegelhalter says, whenever he produces a statistical analysis, he will say how confident he is in the analysis. Sometimes, he adds, that means providing an estimate and then saying “Yeah, but I don’t think it’s very good”.
“It is one of the big things I’ve learned as I got older,” he reflects. “Not just to use the analytic techniques, but to bring that experience and knowledge and judgement in to say, ‘well, actually, how confident are we in our in our analysis?’”
His stance may be supported by recent history, but it’s hard to believe his view is not the product of a deeper belief in simple honesty. “My dogmatism is about trustworthy communication and respect for evidence,” he says. “And I try to live by those principles. I really deeply believe in them at a personal, at a social and at a scientific level.”
David Spiegelhalter, 2025. The Art of Uncertainty: How to Navigate Chance, Ignorance, Risk and Luck. Penguin Books.
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