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We're the programme that looks at the numbers in the news, in life, and in highly ambiguous language.

I'm Charlotte MacDonald.

When you read in the news, you'll often stumble across words that are meant to communicate the probability of something happening.

A terrorist attack is a realistic possibility.

The spread of a certain strain of viruses highly likely.

The relegation of your favourite football team is possible, even if you did get a last-minute equaliser against Liverpool. But when you hear these terms, do you really know what kind of

probabilities they're trying to get across? Do you know how likely, likely is? And what probability

probable is meant to convey? In some cases, it seems you probably

don't. I'm Adam Kacharski. I'm a professor of epidemiology and author of proof the uncertain

science of certainty. Adam has a very healthy obsession with the problem of communicating probabilities,

and it would be remiss of us if we didn't start out by making sure you understand

what the numbers you're going to hear actually mean.

So what does it mean if we say there's an 80% chance of something happening?

Intuitively, we can think of the chance of something happening as the proportion of those events that would come to fruition in reality. So,

for example, if there's 10 events, all of which that have an 80% chance of happening in the next

year, say, on average, we'd expect eight of those 10 to happen. If it's a 10% chance, we'd only expect, on average, one of those 10 events to actually occur.

Okay, so we can express probabilities with numbers, and we can also express them with words like

probable, unlikely, and so on.

Ideally, the words and numbers match up somehow. But that's not always the case.

A real standout example for this kind of problem came in 1951 when a CIA analyst called

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