David Spiegelhalter Quotes

The point is... that you can make these comparisons quite easy... is... 8 [micromorts], running a marathon is... 7, ... 5, 's going to be 400...

We find it very difficult to deal with... low numbers, one in a million, one in a billion... Once I have to start counting the zeros, all intuition and feeling goes. So it's hopeless, and of course we're bad at it. Why should we be good at doing that sort of thing? ...[I]t's more and more reported that people will use this expected frequency format, where instead of talking about... .03 per person year... What does that mean, for heaven's sakes. It's absolutely ridiculous scientific language for something. No, what you say is, out of 100 people... we would expect 3 for this to happen each year. ...You talk about a specific group of people, which you can... draw a... picture of... and that helps enormously. You... want to bring things to... whole numbers, small numbers, preferably between 1 and 100, or between 1 and 50... magnitudes that people have got a feeling for, and... no decimal places, no multiple zeros. You've got to get rid of all of that. You've got to get things to units people can understand, preferably on a scale of 1 to 10.

What we use in the book... are ways which we think might... provide gripping narratives, and yet provide a realistic way of communicating small risks...

Life-expectancy reduced by 1 year = about 30 minutes off your life expectancy for each day with the habit = 1

It’s a common human tendency to attribute a causal effect between different events, even when there isn’t one present...

Gompertz's observation said that between the ages of 25 and 80, your risk of dying increases by about 9% per year. ...[T]hat means that every eight years your risk of dying doubles, essentially. ...[I]t's going to get you in the end. Mathematics proves it. You can't go on forever, because it's this exponential increase in the risk. Amazing, really powerful. That's why you peg out in the end. It's going to get you.

There'a a nice thing about 1/2 hour because an adult life expectancy is 55 to 60 years... is actually a million 1/2 hours. A million 1/2 hours is 57 years. So you have got, not all of you... some of you have got a million 1/2 hours to fritter away.

<nowiki>[</nowiki>s] don't have to get into fantastically complicated statistics. ...It's all just to do with proportions, that's all! It's not a skill. Well, it is a skill in how to tell a story. ...[C]linicians now—we've got some online courses that do this—can learn to do it... Getting a rough idea of magnitudes is very important, and... to avoid words like "chances" and... I'm not even that keen on "s." So I'd much rather say... Experience shows that out of 100 people who match you in these characteristics—They're not you, but would be matching—This is what we would expect to happen, about 60 of them would survive this and... 30 blah, blah, blah... Just as a descriptor, and you could draw a little picture...[etc.] So we've got these possibilities. ...We don't know which one of these you'll be, and then it's very reasonable to tune it: but in your circumstances we... think you're better... other factors... put your chances a little higher... but we can't guarantee it either way.

There is a way... which comes from economics and social science. It was developed by... Frank Knight, and Keynes used this... The distinction between risk and uncertainty...
[R]isk is about things... we... understand... known unknowns, to use Donald Rumsfeld's... great phrase... [something] we can put numbers on, things within... circumscribed situations... A lot of medicine is like this... repetition, a lot of data. ...[I]nsurance is like this ...We know roughly what the chances are, and we can talk about the numbers.
Uncertainty is when... we don't know the numbers, or... deeper... we don't even know... the problem... the options... the possible outcomes...

(DVTs) [normally] happen to around one person per 1,000 each year... out of 5 million people getting vaccinated, we would expect... 5,000 DVTs a year, or... 100 every week. So it is not at all surprising that there have been 30 reports.

Probability was only invented a few hundred years ago. It's not a natural way to think at all. It's extremely difficult and complex. Anything that can help people do it, is of benefit.

If you go to the English Parachuting Association web site... you find this lovely Excel spreadsheet which has got all the deaths... [F]or the last 20 years, 4.6 million jumps, 48 deaths... or 10 in a million. On average, with going up in a plane... I thought there's around 7 or 10 in a million chances of me dying. There's 50 million people in England and Wales... Every day 50 of them have accidental or violent deaths... not to do with their health. So a couple are murdered a day, a few are run over, some people fall off ladders, etc... So that's 1 in a million... Our daily dose of acute risk is a [a 1 in a million chance of dying]. So jumping out of a plane is only about a week's worth. ...[I]n terms of overall mortality... at my age, 59, it's 7,000 micromorts a year in terms of my chances of dying. So an extra 7 or 10 on top of that... [I]t's worthwhile doing... it once....So I did it [parachuted], and I survived.

We need to think slow instead of fast, and resist drawing causal links between events where none may exist.

Psychologists got hold of this lovely idea of why we're trying to do it. I don't care what people do, so I'm not trying to change what they do, particularly. ...It would be nice if they could remember it... get the gist of something... learn something, but I don't even care too much about that. Psychologists have got this great scheme of what, perhaps, we're really trying to do, which is trying to breed some immunity to misleading anecdote, which is... the fact that we're so influenced by idiotic stories we hear on the web, or from our friends and neighbors.

s are very valuable in... low probability, high impact events. Every time you cross the road there is a low probability and high impact that you're going to get run over. ...You take extra precautions to reduce... very small risk to... even smaller. ...[O]n an absolute risk scale, you [might] say, "Oh, I'm not going to bother... It's not worth doing..." but... by making that low risk even smaller, it's... valid... [P]eople discovered this... doing earthquake predictions... [T]he absolute risk... it's always low. They're very unpredictable... but telling people it's 10 times normal, or 100 times normal, people will act... appropriately. ...They won't panic. They won't rush away. ...[I]n Italy ...they ...sleep outside for a bit. ...So in certain circumstances relative risk can be very valuable... [U]sing both in... situations... with very small risks.., where... consequences are... severe... [and] the cost of the intervention, the action, is... minimal. Taking a bit more precautions, being a bit more careful... not putting a big investment into making a very small risk even smaller.... not walking under ladders... a low-cost change in your behavior to make a small risk even smaller... [A]bsolute risks really don't deal well with that, because you're talking 0.000...