The Herald has been running a 'Poll of Polls' to look at what all the polls coming out say about how Parliament will look come October. Thomas is joined this week by the man behind the data, the Herald's Chris Knox, to discuss how polling works, how that informs the Poll of Polls, and some of the fiddlier bits of polling such as margins of error, electorate polling, and if they can become self-fulfilling prophecies. 

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