Just before this BBC podcast gets underway, here's something you may not know.

My name's Linda Davies and I Commission Podcasts for BBC Sounds.

As you'd expect, at the BBC we make podcasts of the very highest quality featuring the most knowledgeable

experts and genuinely engaging voices. What you may not know is that the BBC

makes podcasts about all kinds of things like pop stars,

poltergeist, cricket, and conspiracy theories and that's just a few examples.

If you'd like to discover something a little bit unexpected, find your next podcast over at BBC Sounds.

Hello and welcome to More or Less, the program that gives numbers a bracing ice bath followed by an invigorating backrob. This week the former Home Secretary

Amber Rod said she doesn't know how many people may have been threatened with deportation

despite having the right to live in the UK, so we'll take

a crack at the problem. Also a popular guest on question time.

Nigel Farage. And the Queen of Too Much Information, Data Journalist Mona Chalaby.

But first, this week the Health Secretary, Jeremy Hunt, made a statement in the House of Commons to say that

due to an administrative mistake, 450,000 women aged 68 to 71 were not invited to their final breast cancer screening.

Our current best estimate, which comes with caveats as it's based on statistical modeling rather than patient reviews and because there is

currently no clinical consensus about the benefits of screening for this age group is

that there may be between 135 and 270 women who had their lives shortened as a result.

Well where does a number like that come from?

We turn to Cambridge Professor David Siegelhalter,

president of the Royal Statistical Society and perhaps more importantly a leading medical statistician.

We asked him to stop what he was doing and tell us, please,

if this number of up to 270 affected women was reasonable. So in one hand he had the back of an envelope

...