A Polemic on Political Polls, by dnd

A couple of days ago I was watching the local news when the anchor said that McCain was now leading Obama in Colorado 44% to 42%. I squinted to see the fine print on the screen on the screen which revealed a margin of error of ± 3%. Now I don’t expect journalists to be math wizards, but a spread of 2% with a margin of error of 3% indicates that it’s impossible to tell who’s ahead.

The margin of error is what is referred to mathematically as a confidence interval. This means that if they say a candidate has 44% of the vote ± 3%, one can say that the candidate enjoys somewhere between 41% to 47% of the vote. But you can’t say for sure where in that interval. There’s more. For every confidence interval there is a confidence level, typically 95% for political polls. This means that you’re 95% confident that your confidence interval is correct.

The question now becomes how many people do you poll to achieve some particular margin of error? I won’t go into the details of the central limit theorem here, which is where the number comes from, but suffice to say, the more people you poll, the smaller the margin of error is. The good news it that a relatively small number of people polled will give you a good margin of error. The bad news is that the central limit theorem places some conditions that are difficult to stick with in polling.

The margin of error is the only type of polling error that can be quantified, and consequently is the only error reported. However there are other types of error in polling. Coverage error, measurement error and non-response error are also considered by professional pollsters. Coverage error refers to not being able to contact you. You may not have a land line, you may be on vacation, or you may be stationed in Iraq. Measurement error has to do with how the survey is presented: wording, question order, response options, mistakes by the interviewer, the interviewee jerking the interviewer’s chain, etc. Non-response error is people who let the answering machine pick up, have caller ID, or simply tell the interviewer “no.”

Consequently the typical poll has a biased sample of the voting population. Sophisticated pollsters have ways for weighting the results based on these biases, but these methods can only be applied if the biases are known. For example, asking the age, gender, political affiliation, education, etc. are important questions.

Presidential polls that report national sentiment are fun, but don’t tell the correct story since we don’t elect presidents by popular vote. And timing is everything. Political junkies find this hard to believe, but a significant percentage of the electorate won’t pay any attention until after the conventions. Consequently the poll results may suffer the “I dunno” factor.

So for the time being, poll results reported by the press are pretty much a parlor game. Campaigns have much more sophisticated, targeted polls, since these serve as information about how to spend their resources. But they ain’t talkin’.

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54 Comments

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54 responses to “A Polemic on Political Polls, by dnd

  1. I have such a love/hate relationship polls it’s unreal.

  2. Karolenna

    Has anyone on here ever been contacted by a pollster the election? I have not. I have a land line and I have a cell phone, but I have not been contacted. Is it because somehow they already know how I think?

  3. Horsedooty

    I don’t bother with them this far out. Maybe and only maybe after the convention. Thanks for the good post though, D nd

    ¡yo soy Horsedooty!

  4. I’ve been contacted for “issue” polls, but never about candidates.

  5. Karolenna

    Just got off the phone with my daughter. She says her mother-in-law in SW Ohio does not know if she can vote for a Muslim. Can you believe that? This woman is an accountant! Did it take this election to bring out the stupidly of so many people?

  6. dnd

    Karolenna,
    The reason you probably haven’t been contacted is that is only takes around 1000 people to get the margin of error they seek. If you factor in coverage error and non-response error, they probably only have to contact a few thousand to complete the poll.

    “Push” polls are different. They’re trying to influence your vote so they are very targeted and contact many more people.

  7. “Did it take this election to bring out the stupidly of so many people?”

    Apparently so!

  8. dnd

    One other thing to be wary of is the recent confusion over the Gallop polls that, depending on the poll showed either McCain or Obama ahead. It was confusing due to the “likely voter” vs. “registered voter” results. The media reports only that, the pundits weigh the “likely voter” more heavily, but the pollster clarified the importance:

    “Registered voters are much more important at the moment,” Gallup chief Frank Newport said. He said McCain’s lead among likely voters suggests “the possibility’s there that Republicans can get energized.”

    http://www.usatoday.com/news/politics/election2008/2008-07-28-poll_N.htm?loc=interstitialskip

    The other subtext here is the methods pollsters use to weight polls because of non-quantifiable errors. These methods are proprietary and are what separates polling organizations. Gallop has been criticized before for results which stem from their proprietary methods.

  9. Karolenna

    I am angry as hell at those still living in the past and not looking forward. This notion that they are going to write in a candidate who does not have a chance in hell to win angers me to the bone. They choose to throw away their vote.

  10. Voting out of spit is just stupid and a waste!

  11. dnd

    The funny (or sad) thing about protest votes is that the candidate whom you’re protesting will never receive the message. It may make the protester feel better, but it’s basically throwing away your vote.

  12. dnd

    Sen. Ted Stevens to be indited by a federal grand jury today. Seven counts of making false statements to an investigator. Uh-oh.

    Maybe he’ll make it to Bush’s pardon list.

  13. Voters who throw their votes away are immature and disrespectful to the men and women before us that worked and sacrificed so that all American would have an equal right to vote. It’s the ultimate slap in democracy’s face.

    It is really disgusting.

  14. dnd

    The best, and most effective protest votes are when you have a corrupt pol like Ted Stevens, vote for the other guy!

  15. dog's eye view

    Seriously good post. Seriously.

  16. 7 counts against Stevens, being announced right now.

  17. Uhm….just got up from a nap….or am I dreaming? Mr. “Bridge to No Where” Indited?

  18. Polling- I got push polled once but hung up before the guy could finish- I didnt get mad about the poll- I just got bored!

  19. dnd

    Hip,
    I love getting push poll calls. It’s pretty clear pretty soon what they are, so it’s fun to mess with them.

  20. Push polls-

    Would it change your mind about Raplh Reed’s opponent if you found out he was a heroin dealing pedophile?

  21. Karolenna

    I was reading what Howard Fineman said about Virginia Gov. Tim Kaine. He says that he and Obama share political consultants.

    “The Benenson Group, headed by Joel Benenson, is advising Obama. The group’s principal consultant, Peter Brodnitz, who gained his reputation handling Sen. Jim Webb of Virginia, is advising Kaine.

    These consultants have two calling cards: [I kinda like this] an extremely shrewd, detailed understanding of how to use new media to sample opinion, and an eagerness to operate on turf considered too culturally conservative for Democrats.

  22. Karolenna

    Forgot to provide the link in case anyone is interested in the complete piece. Some interesting observations.

    http://www.msnbc.msn.com/id/25912762/

  23. Here’s The Times article on Stevens:

    Alaska Senator Is Indicted on Corruption Charges

    http://www.nytimes.com/2008/07/30/washington/30stevens.html?_r=1&oref=slogin

    Stevens must have been so far over the line if the Bush justice dept couldn’t turn it’s head!

  24. dnd

    5.8 magnitude quake hits L.A. No reports of major damage. Amazing.

  25. dnd

    Here’s the scoop on the earthquake from the USGS’s National Earthquake Information Center in Golden Colorado:

    http://earthquake.usgs.gov/eqcenter/eqinthenews/2008/ci14383980/

  26. Only been in one earthquake, when I lived in SF about 25 years ago, the building shook really hard then stopped. I called everyone I knew back east to brag about my first quake.

  27. dnd

    I was in Salt Lake City during the 1974 earthquake. Fortunately it was mild, as the Wasatch fault runs right through town. If it’d been a big one all hell would’ve broke loose.

    I was in another one in Tokyo in 1995. Scared me to death, but the locals were calm and didn’t think much of it.

  28. Been in a lot of earth quakes, they can be really scary. You learn in stop-go traffic to never get stuck on a bridge or under an overpass, for fear if a quake hits you are in a very bad place.

  29. Chef Sheila

    I have had the privelege of experiencing earthquakes steming from different faults and or active volcanos……very insteresting. how some shake side to side, some riple, and some jump very fast like a salt shaker.

    I was in three notables. One in 1968 that caused some serious mud slides on San Diego.

    One in Pina Tomari italy. That one (HARD) swayed my apartment on the 4th floor….well no wonder I got an aparment with a great view cheap.

    One here in Puget Sound in 2000. It was the biggest at 6.8 I will never forget the obtuse thoughts running through my head while it was happening.

  30. Chef Sheila

    dnd, thanks!!

    I really learned something today. Polls Not was frustrating as I used to think.

  31. dnd

    Sra Burrito,
    I have some friends that were in SF during the Loma Prieta earthquake. Fortunately they were home waiting for the World Series to start. But they share your view it’s not good to get stuck on a bridge or under an overpass.

  32. dnd

    Thanks Shelia and everybody else. Polling is part science, part art, and part politics. I’m most interested in the science part because that’s my background. Fun stuff. Hard to interpret.

  33. Chef Sheila

    David Horsey

    “If candidates could Draw, we wouldn’t need Cartoonists”

    http://seattlepi.nwsource.com/horsey/viewbydate.asp?id=1794

  34. Horsedooty

    several years ago a fellow tech rep and I spent a week in southern California working on some problem machines in the area. This fellow with me did not have to travel much in his job. He was from the home office in Fla and he was in a panic every time we went under a bridge or over an over pass. It was amusing at first but after about Wed it got old. We had no problems.

    ¡yo soy Horsedooty!

  35. My Husband was traveling in SF and was on that double decker about an hour before it pancaked (Loma Prieta quake)…..I couldn’t reach him because he decided to get to take an earlier flight he was in the air.

    It’s really amazing how small choices can change your life.

  36. Chef Sheila

    I came in with President Bush. It was surreal and frightening even after a couple of days. Burrito, I can’t imagine how you felt in hindsight.

  37. I’ve been through 4 earthquakes, and have slept through every single one of them.

    They were minor though, I think all 4’s.

    Hope you all are well this morning.

  38. dog's eye view

    Good morning all.

    Have never been through a California earthquake, and it always seemed the worst of guest behavior to express interest in doing so.

    Did experience a mild earthquake while in Richmond, VA — middle of the night, felt like a truck passing below but no vehicle appeared.

    Lived in Richmond during Hurricane Isabel, which did a lot of damage 100 miles inland — took down many of Richmond’s famous old trees along Monument Avenue and pulled down the tree fronting our apartment building — onto an unwary neighbor’s car. Power out for 3 days and enjoyed a neighborhood block party (hey, we had a cul de sac due to the downed tree) since we had to cook up the food asap. Rather fun, but HOT.

    Will have to hunt up the pix and share them sometime.

  39. dog's eye view

    Here is an interesting guy who lived a full life. Bud Browne, began shooting 8m and later 16mm footage of surfers from 1940s on. Eventually made a living at shooting and displaying his films. Bungee jumped until he was 86.

    http://www.latimes.com/news/obituaries/la-me-browne29-2008jul29,0,709656,full.story

  40. Chef Sheila

    Good morning everyone!

    I’m going to be busy at least one more day. Today is a dinner and tomorrow the Big Guy goes fishing. Ahhhhh,,,,,,,,life will calm down a little after that.

    But until then…..Shake a leg. LOL

  41. Karolenna

    Gee, I feel cheated. I’ve never been in an earthquake!

  42. Chef Sheila

    LOL Karolenna,

    It ain’t fun and kind of surreal, but I bet you have been through something that some of us haven’t? Like tonado warnings and or something like it?

  43. Karolenna

    Sheila,

    On Mother’s Day my Mom was visiting. We were going to my sister’s house for a dinner. The sirens started going off and Mom, who lives in the country, was scared to death because she had not heard them before. I have a bi-level house so being in the basement is not underground, but I put her in a chair in what I thought was the safest place. Yes, we have many tornados go around us in Central Ohio.

  44. Chef Sheila

    Wow! The first time I was in the path of one, I did everything I was supposed to. All my work mates laughed at me for “overreacting” But I didn’t know that everyone else just waits until the they hear the signs of one, before they go into the basement. …

    I proclaimed myself a Tornado Warning Virgin. I hope I never have to say I actually went though one. I’d rather be in an earthquake~

    Glad yours was a drive by too!

  45. Chef Sheila

    The title speaks for itself…..

    Canadian Ice Shelf Loses 7-Square-Mile Section

    http://www.huffingtonpost.com/2008/07/30/canadian-ice-shelf-loses_n_115777.html

  46. Chef Sheila

    Brian,

    I knew it!!! The McCain attacks and the Press’s non-reaction have all the earmarks of Karl Rove…..!@#$

    Well the fight has really begun.

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