Friday, February 29, 2008

Polls and Polling


We all know the difference between the polls and polling. But we may not realize what a difference there is in the polling.

First though, you should always be mindful of the concept of Alpha in any Poll. An alpha number of 5 means that there is a 5% chance that these numbers mean absolutely nothing. That's the reason some polls fall outside of the pack. But assuming that your information is inside the 95% confidence range, then the next thing you need to watch out for is a poll with likely voters or LV. An LV means that the polling organization is predicting the turnout and the complexion of the turnout.

Here's today's new Zogby poll which says:

Reuters/C-SPAN/Houston Chronicle Poll:
Obama Builds Lead Over Clinton in Texas,
But Dem Race Too Close To Call in Ohio

Texas - Democrats

Clinton 42%
Obama 48%
Gravel <1%
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If you look at the last five polls in Texas , you will see that one, Insider Advantage, has Clinton up by 4. But the average of all five today show Obama with a lead of 2.4. Assuming that alpha is not at play, why the big difference?

You must look deeper into the poll to see why. The Insider Advantage poll has decided that the likely voters will be fairly represented by (225) white,(130) black, (219) hispanic voters. That W/B/H ratio is 39/13/38. Clinton is ahead 53-39 in Hispanics and Obama is ahead 75 to 14 with Blacks.

When you go deeper into the Survey USA Poll ,which shows an Obama lead of 4, the W/B/H ratio is 47/21/28.

Look deeper into the Rasmussen Poll which has Obama up by 4 and you see that the W/B/H ratio is 57/16/27.

When you sort through the cross tabs of the PPP poll ,which shows a tie, the ratio is 45/22/29

I'm not sure why our media doesn't dig into the polls. Probably they do, and they figure that we won't understand it. Maybe they figure that this kind of information should stay in the campaigns and with the experts.

But it makes running a big headline saying that Obama is building a big lead a little bit misleading. If you don't know the crosstabs of the poll, you really don't know much.
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But practically all of us understand this:
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If you put more Clinton supporters in the LV poll, you get a better number for Clinton. If you put more Obama supporters, he ends up with a big lead.

I don't know what the real W/B/H mix is going to be in the Texas Primary, and apparently, neither do the pollsters. But if we use the PPP poll as a yardstick, we can perhaps come to this metric.
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If the the second number is higher than 22, that's good for Obama, if the third number is higher than 29, that's good for Clinton.

You can do the same thing with age. In the Insider Advantage poll where Obama is behind, 20 year olds represent only 10% of the total. In the Survey USA poll where Clinton is behind, that number is closer to 20%. (tabs are for different ages)

So when it comes down to polls that have a LV next to them,

watch out.

The "difference" is the difference between the Polls and the Polling.

It's the difference between the talkers,

and the walkers.

And walking is where it's at this year..

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2 Comments:

Anonymous Anonymous said...

The size of the headlines greatly exceeds the point spread. I used to remember when the networks wouldn't call the election until the polls closed in CA. Now it seems that they are calling the election before the polls even open.
Best,
FM

12:10 PM  
Blogger OZ said...

I made a few grammatical changes to the post in the afternoon.

Since this post was written, there are already several new polls which show Obama leads.

Once again, projecting the complexion of the turnout is critical to whether of not the polling results will predict the actual polls.

2:07 PM  

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