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Reply #4: TruthIsAll, this is GARBAGE; you don't understand margin for error [View All]

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Awsi Dooger Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Nov-10-04 11:09 PM
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4. TruthIsAll, this is GARBAGE; you don't understand margin for error
Sorry to be so blunt, but it's accurate and therefore this mathematical exercise is worthless. Try finding a clincher that's not so easily spun into the toilet.

MOE is applied to EACH number, not just the MARGIN between the two candidates. You are making the most basic of mistakes, something network anchors and talking heads fall prey to repeatedly.

Let's look at this example, a hypothetical state poll, let's say Florida:

Kerry 50%
Bush 49%

Margin for error 4%

Now let's say Bush wins 52-47%. That is NOT outside the margin for error, despite the 6 point gap. The MOE is applied to EACH of the two numbers. Therefore, Kerry's support is expected to range from 46-54% and Bush from 45-53%. That is where the 95% confidence level kicks in. It is statistically more likely Kerry will be ahead by 1, and so on, than down 4 or 5 or 6, but all fall within the MOE.

Don't take my word for it. Look it up on the internet. Here is the first link in a search I just did: http://momentlinger.typepad.com/momentlingeron/2004/08/understanding_p.html

Besides using the most favorable exit polls for Kerry, like the absurd 57-41 edge in New Hampshire, and even if your initial use of MOE had been correct, you are also understating margin for error among state polls. You are obviously using 3%, based on where Ohio and Wisconsin fit on your list. The margins differed by 4%, yet are listed outside the margin for error on your list. The company that does nationwide exit polls states very clearly on their website that state exit polls include a 4% margin for error, not 3%: http://www.exit-poll.net/faq.html#a15

"What is the Margin of Error for an exit poll?
Every number estimated from a sample may depart from the official vote count. The difference between a sample result and the number one would get if everyone who cast a vote was interviewed in exactly the same way is called the sampling error. That does not mean the sample result is wrong. Instead, it refers to the potential error due to sampling. The margin of error for a 95% confidence interval is about +/- 3% for a typical characteristic from the national exit poll and +/-4% for a typical state exit poll. Characteristics that are more concentrated in a few polling places, such as race, have larger sampling errors. Other nonsampling factors may increase the total error."
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