On my return from Sri Lanka last week, I read the back issues of the Cleveland newspapers and found that a big story was the vicious beating of a middle-aged white man by a group of six black teenagers who had accosted him while he was on a walk in his neighborhood. The man was saved from possible death because of the alarm raised by a resident (who is a faculty member at Case) who had observed the assault from his home front window and raised the alarm, which caused the attackers to flee.
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The fourth time I was empanelled was for a criminal case involving charges of felonious assault where the defense said that it would argue self-defense. Once again, there was an oral voir dire, which included questions about whether we had ever been involved in any physical altercation.

It was during the voir dire that I ran into a problem. One of the prosecuting counsel asked if the jurors would be willing to convict a person on the facts of the case even if they felt the law under which the person was being prosecuted was unjust. It was clear that he expected you to answer ‘yes’ to this question. We have all seen at least some courtroom dramas where the judge instructs the jury on the law to be applied and the jury is asked to judge based only on the facts of the case, and not to judge the validity of the law itself.
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By a coincidence, while writing and posting my series on the law and religion in public schools, I was also called for jury service and spent the better part of the week of November 5, 2007 in the Cuyahoga County Common Pleas Court in downtown Cleveland.

I feel strongly that the jury system is one of the greatest inventions of modern society and has been the foundation for democracy and creating and preserving freedoms. So I feel that to serve on a jury is a privilege and do not resent doing my time on the jury though it does involve some minor inconveniences and disruptions in work and home routine.

This was the third time I have been called for jury duty but I have yet to actually sit in on a case. For those not familiar with how it works, at least in Cuyahoga County where I live, when you are called for jury duty to the Common Pleas Court, it is not for a particular case but to be part of a large pool of jurors that serve many courts. So much of the time is spent waiting until your name is randomly called as needed if a case cannot be settled and should need to go to trial.
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Ever since election day on November 6, 2007 news reports in Cleveland have been obsessing over the fact that the results were delayed by a couple of hours due to a systems crash that required the backup to kick in.

I am puzzled by this obsession with speed in elections. Why is there such a rush to get election results out so quickly? This drive for speed seems particularly paradoxical in the US where election campaigns are dragged out longer than in any other country and where there is a long time interval between voting day and the newly elected person actually taking office. New office holders typically take over at the beginning of the following year, allowing for a two-month transition period. The new president does not take the oath of office until January 20.
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(I am taking a break from original posts due to the holidays and because of travel after that. Until I return, here are some old posts, updated and edited, for those who might have missed them the first time around. New posts should appear starting Monday, January 14, 2008.)

As the 2008 election season gets into high gear, we will get inundated with the results of opinion polls. Many of our public policies are strongly influenced by these polls, with politicians paying close attention to them before speaking out.

But while people are inundated with opinion polls, there is still considerable misunderstanding about how they work. Especially during elections, when there are polls practically every day, one often hears people expressing skepticism about polls, saying that they feel the polls are not representative because they, personally, and all the people they know, have never been asked their opinion. Surely, they reason, if so many polls are done, every person should get a shot at answering these surveys? That fact that no pollster has contacted them or their friends and families seem to make the poll results suspect in their eyes, as if the pollsters are using some highly selective group of people to ask and leaving out ‘ordinary’ people.

This betrays a misunderstanding of statistics and the sampling size needed to get good results. The so-called “margin of error” quoted by statisticians is found by dividing 100 by the square root of the size of the sample. So if you have a sample of 100, then the margin of error is 10%. If you have a sample size of 625, then the margin of error drops sharply to 4%. If you have a sample size of 1111, the margin of error becomes 3%. To get to 2% requires a sample size of 2500.

Clearly you would like your margin of error to be as small as possible, which argues for large samples, but your sample sizes are limited by the cost and time involved in surveying people, so trade offs have to be made. Most pollsters use samples of about 1000, and quote margins of error of 3%.

One interesting point is that there are statistical theorems that say that the sample size needed to get a certain margin of error does not depend on the size of the whole population (for large enough populations, say over 100,000). So a sample size of 1000 is sufficient for Cuyahoga County, the state of Ohio, or the whole USA. This explains why any given individual is highly unlikely to be polled. Since the population of the US is close to 300 million, any one of the 1000 people I may personally know has only a 0.00033% probability of being contacted.

We know that a poll tells us that 54% of Americans say that “I do not think human beings developed from earlier species.” The sample size was 1000, which means a margin of error of about 3%. Statistically, this means that there is a 95% chance that the “true” percentage of people who agree with that statement (i.e., the number we would get if could actually ask each and every person on the country) lies somewhere between 51% and 57%.

Certain assumptions and precautions go into interpreting these results. The first assumption is that the people polled are a truly random sample of the population. If you randomly contact people, that may not be true. You may, for example, end up with more women than men, or you may have contacted more old people or registered Republicans than are in the general population. If, from census and other data, you know the correct proportions of the various subpopulations in your survey, then this kind of skewing can be adjusted for by changing the weight of the contributions from each subgroup to match the actual population distribution.

With political polls, sometimes people complain that the sample sizes of Democrats and Republicans are not equal and that thus the poll is biased. But that difference is usually because the number of people who are officially registered as belonging to those parties are not equal.

But sometimes pollsters also quote the results for the subpopulations in their samples, and since the subsamples are smaller, the breakdown data has greater margin of error than the results for the full sample, though you are often not explicitly told this. For example, the above-mentioned survey says that 59% of people who had high school education or less agreed that “I do not think human beings developed from earlier species.” But the number of people in the sample who fit that description is 407, which means that there is a 5% uncertainty in the result for that subgroup, unlike the 3% for the full sample of 1000.

But a more serious source of uncertainty these days is that many people refuse to answer pollsters when they call and it is not possible to adjust for the views of those who refuse. So although the pollsters do have data on the numbers of persons who hang up on them or otherwise refuse to answer, they do not know if such people are more likely or less likely to think that humans developed from earlier species. So they cannot adjust for this factor. They have to simply assume that if those non-responders had answered, their responses would have been in line with those who actually did respond.

Then there may be people who do not answer honestly for whatever reason or are just playing the fool. They are also hard to adjust for. This is why I am somewhat more skeptical of surveys of teens on various topics. It seems to me that teenagers are just the right age to get enjoyment from deliberately answering questions in exotic ways.

These kinds of biases are hard, if not impossible, to compensate for, though in serious research the researchers try to put in extra questions that can help gauge whether people are answering honestly. But opinion polls, which have to be done quickly and cheaply, are not likely to go to all that trouble

Because of such reasons, polls like the Harris poll issue this disclaimer at the end:

In theory, with probability samples of this size, one could say with 95 percent certainty that the overall results have a sampling error of plus or minus 3 percentage points of what they would be if the entire U.S. adult population had been polled with complete accuracy. Sampling error for subsamples is higher and varies. Unfortunately, there are several other possible sources of error in all polls or surveys that are probably more serious than theoretical calculations of sampling error. They include refusals to be interviewed (nonresponse), question wording and question order, and weighting. It is impossible to quantify the errors that may result from these factors.

For all these reasons, one should take the quoted margins of error, which are based purely on sample size, with a considerable amount of salt.

There is one last point I want to make concerning a popular misconception propagated by news reporters during elections. If an opinion poll says that a sample of 1000 voters has candidate A with 51% support and candidate B with 49%, then since the margin of error (3%) is greater than the percentage of votes separating the candidates (2%), the reporters will often say that the race is a “statistical dead heat,” implying that the two candidates have equal chances of winning.

Actually, this is not true. What those numbers imply (using math that I won’t give here) is that there is about a 75% chance that candidate A truly does lead candidate B, while candidate B has only a 25% chance of being ahead. So when one candidate is three times as likely as the other to win, it is highly misleading to say that the race is a “dead heat.”

POST SCRIPT: Inflated value of religion

Many people have an inflated sense of the value of religion that simply falls apart on close examination. For example, Mike Huckabee said the following: “The Ten Commandments form the basis of most of our laws and therefore, you know if you look through them does anybody find anything there that would be all that objectionable? I don’t think most people would if they actually read them.”

He says this as if it is obviously true. But Ed Brayton shows how absurd this is.

As the interminable political primary season drags on, I have to say that the Republican race has proved to be far more interesting than the Democratic one. We have the drama of Mitt Romney trying to fend off unease over the issue of his Mormon religion and worrying about how his switching of positions to pander to the Christianists in the party will play out, serial philanderer Rudy Giuliani having to deal with one sex and money and corruption scandal after another, Ron Paul irritating the rest of them and the media with his constitution-based attacks on war mongering producing a remarkable response for someone considered a nobody, the once great hope Fred Thompson sleepwalking through the primaries, media darling John McCain looking more and more like a has-been, and those lovable scamps Tom Tancredo and Duncan Hunter (can anyone tell them apart?) falling over themselves in seeing who can hate immigrants the most. As if that was not enough fun, for the last debate they brought in surprise contestant Alan Keyes (yes, Alan Keyes!), an egomaniac of such giant proportions compared to whom even the insufferable Giuliani comes across as modest and self-effacing.

But the latest development is the sudden vaulting into the top tier-ranks of Mike Huckabee. In many ways, he was always a natural to lead the pack because he had, on the surface, few of the negatives associated with the others and all the positives. He was a southerner, a former governor, a Baptist preacher, and has long held the kinds of views that the religious right wants its leaders to have on issues like abortion and gays. He may not have been as hard line as they might have wished on issues like not raising taxes or hating immigrants, or as enthusiastic about supporting the Bush wars and torture that the crazies in his party would like. But these drawbacks were merely matters of degree and one would have thought that given the strong negatives of the other choices that Republican primary voters had, he would have been the one they liked most. So the surprise for me is not his rise in the polls but why it took so long.

But what is really interesting is the reaction to his rise from the power brokers of the Republican Party. They have responded with alarm and brought out the long knives, trying to cut Huckabee down. Former Bush speechwriter David Frum piles on, essentially calling him a moron and even obliquely suggesting Huckabee of being a kindred spirit of Scientologists.

So why all this angst about this southern Bible thumper, who seems to be very similar in background and views to George W. Bush, the president the Washington insiders love, even if he will go down as the worst president in US history and whose current approval ratings are in the sewer?

Kevin Drum at the blog has the best explanation that I have seen so far for this Huckabee hate fest among leading conservatives:

There are a variety of ostensible reasons for this: lack of foreign policy bona fides, too compassionate for their taste, too willing to consider spending money, etc. But I think the real reason is simpler: as with blogosphere conservatives, mainstream conservatives are mostly urban sophisticates with a libertarian bent, not rural evangelicals with a social conservative bent. They’re happy to talk up NASCAR and pickup trucks in public, but in real life they mostly couldn’t care less about either. Ditto for opposing abortion and the odd bit of gay bashing via proxy. But when it comes to Ten Commandments monuments and end times eschatology, they shiver inside just like any mainstream liberal. The only difference is that usually they keep their shivering to themselves because they want to keep everyone in the big tent happy.

But then along comes Huckabee, and guess what? He’s the real deal. Not a guy like George Bush or Ronald Reagan, who talks a soothing game to the snake handlers but then turns around and spends his actual political capital on tax cuts, foreign wars, and deregulating big corporations. Huckabee, it turns out, isn’t just giving lip service to evangelicals, he actually believes all that stuff. Among other things, he believes in creationism (really believes), once proposed that AIDS patients should be quarantined, appears to share the traditional evangelical view that Mormonism is a cult, and says (in public!) that homosexuality is sinful. And that’s without seeing the text of any of his old sermons, which he (probably wisely) refuses to let the press lay eyes on.

John Cole, a conservative who has watched with dismay the Republican Party pandering to the religious extremists, also lists some of the nasty things that are being said about Huckabee and enjoys a moment of schadenfreude:

I simply can not tell you how much I am enjoying this. The GOP has been pandering to these stupid bastards for years, and every time I pointed it out I was called “anti-Christian” or something or other. Those of us who saw what the party was becoming were told to shut up, that it was good politics.

Enjoy your new GOP, folks. And here is something else to think about – are the evangelicals going to support Romney or Giuliani if you do manage to trash Huckabee enough to secure the nomination for them? Will the eye for an eye crowd learn to forgive and forget? Have fun!

Next: Meet the Villagers: The real political divide in America

POST SCRIPT: Torture

One of the most depressing phenomena of recent times is how so many people who should know better are willing to defend the use of torture, using legalistic quibbling to justify barbaric practices that would have been unhesitatingly condemned if the identities of the torturers and the tortured were switched.

Tom Tomorrow as usual says it most concisely.