Hello and welcome to more or less election podcast 4, a collection of interviews that were

first broadcast on BBC Radio 4's PM programme with Eddie May. Tim Harford and Ruth Alexander

have been taking it in turns to make sense of the numbers being used by politicians.

On Friday, April the 24th.

Ruth Alexander from Radio 4's More or Less is here, Ruth, you've been looking at the

opinion polls.

Yes, that's because we had an email to email address more or less at bbc.co.uk if anyone

else can be tempted.

From a listener called Martin, who asked we thought a rather good question, he said, every

day we're getting polls.

How come some say one party in the lead by two and some say the other party in the lead

by two, surely they should all be the same?

Well the reason they're not is because the pollsters aren't asking everybody in the

UK how they're going to vote, they're asking a representative sample, often it's just

about one or two thousand people and the probably the best way to think about this is to picture

a night pan of voter soup bubbling away on the hob, a metaphor I borrowed from a professor

of statistics Kevin McComway from the Open University who is a keen untold but not always

competent cook.

Anyway, taking an opinion poll is really like sampling a spoonful from this voter soup

to see how the whole pound full tastes.

But if you skim the surface, you know you might just get croutons or you might end up

with just a spoonful of mushrooms.

...