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Hello and welcome to more or less on the BBC World Service.

Your weekly ration of numerical nutrition. I'm Jan Wong.

This week we'll be reporting on a rogue Indian statistic which has fueled a full scale political row.

Why in his address to the Punjabi University Rahul said seven out of certain youth in Punjab were drug addicts?

But first, this week six Italian scientists and one ex-government official were sentenced to jail for manslaughter.

Why? Because they made overly reassuring statements before this happened.

A big earthquake in Italy, there's widespread damage to a medieval town where many are dead.

The earthquake which hit the Italian town of Laquila in March 2009 killed 309 people.

Perhaps we shouldn't be surprised that amid the grief and anger which followed, some in Italy wanted to apportion blame.

But is it right to blame the scientists? Well, at its heart this is a story about numbers and probability.

So let's start with an obvious question. Is it actually possible to predict earthquakes?

The short answer is no. That's Ian Main, professor of seismology and rock physics from the University of Edinburgh, Scotland.

And also a member of a committee on earthquake forecasting following the tragedy in Laquila.

In our sense we can forecast that they are almost certain to happen with a very low probability.

Maybe once in a hundred, once in a thousand years depending on the size of the earthquake and a given zone.

And that's a hazard that's there all of the time. A fault can go at any time. But we know it's going to happen.

And in the case of this earthquake in Italy it was preceded by a whole series of smaller tremors.

I assume that that means you can change the estimate of probability that a major earthquake will happen after that. It changes the equation somewhat.

Yes, one of the things that's fairly consistent about earthquake population dynamics is that they often occur in clusters.

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