Last week, I discussed some of the sampling problems that can crop up in pollsters' work.  My first article showed how the problem of bias is intrinsic to stratified sampling.  My second article expanded the discussion to demographic weighting and cluster sampling.

Today, I'm going to resume the discussion of polling problems by looking at the media's new tactic of using polls-of-polls to resolve the sometimes conflicting information from polls that get reported on an hourly basis.

There's more... 

Here at Overdetermined, we've been playing with the idea of using a ticker module for micro-posts.  Here's a great example of the reason to have something like that:

Over on 538 today, Nate Silver took a look at today's IBD/TIPP national tracking poll, which shows Obama with a 1-point lead over McCain.

Yes, you heard that right, a 1-point lead.

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This week, I’m going to be spending some time discussing some of the problems with current polling methodology.  The numbers we’re seeing in today’s polls may not accurately represent the real shape of the electoral landscape. 

The stratified sampling problem has been almost completely ignored, in favor of more easily digestible problems like the Bradley Effect and cell-phone user undersampling.  Unfortunately, the stratified sampling problem may prove to be more influential than either of those concerns.

I’m going to do my best to keep this post understandable for anyone with an interest in polling, but be forewarned: I’m dealing with a deep-seated technical problem that suffuses the entire polling industry.  If the stratified sampling problem were easy to understand and manage, we wouldn’t be having this conversation.

There's more...