Sunday Supplement - Margin of Error

Do you trust opinion pollsters? Probably not as much as you trust doctors or teachers.

Peter Snow on the set of the BBC Election Night programme

On the other hand, probably more than you trust journalists or politicians. How do we know that? Thanks to an opinion poll, of course.

The polls will be monitored ever more intensively the closer we get to the next general election. But to what extent can they really be trusted?

In a new series for The Westminster Hour first broadcast in October 2004, Peter Snow, that legend of the swingometer, investigates the polling industry in Margin of Error.

In Part One, Peter explores the difficulties faced by opinion pollsters and how they try to get around them.

In Part Two, Peter explores how the Internet is being used in opinion polling and the battle raging between web-based pollsters and their more traditional rivals.