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April 30th, 2011 (Permalink)

Check it Out

Here's a very interesting article by Chris Mooney on the psychology of confirmation bias, and how people tend to reject scientific research that challenges their political beliefs and desires.

Source: Chris Mooney, "The Science of Why We Don't Believe Science", Mother Jones, 4/18/2011


April 29th, 2011 (Permalink)

Blurb Watch: The Conspirator

Blurb Context
"PROVOCATIVE. PULSES WITH THE THRILL of discovery. The shining star is Robin Wright."
-Richard Corliss, TIME
In [Robert] Redford's starchy but provocative [movie], Union war hero Frederick Aiken (James McAvoy) is persuaded…to defend Mary Surratt (Robin Wright) at her trial [for conspiring to assassinate Abraham Lincoln]. … Thirty years after his directorial debut with the Oscar-winning Ordinary People, Redford comes to this period piece with a visual style that is both stately and obvious. … He might have chosen his leading player more wisely: McAvoy…plays Aiken as a bit too callow and tentative. The rest of the cast does fine by their roles. … The shining star is Wright, who brings drama and beauty to every role just by staring into the camera. … Wright's performance is the key to a movie that pulses with the sick thrill of historical discovery.
Source: Ad for The Conspirator, The New York Times, 4/24/2011, p. AR 12 Source: Richard Corliss, "The Conspirator: Abraham Lincoln's 9/11", Time, 9/17/2010

April 27th, 2011 (Permalink)

"It's tough to make predictions, especially about the future."

Cannot predict now

A new study, which purports to show precognition, is getting a lot of attention from skeptics. Michael Shermer's latest Scientific American column gives a brief account of the experiments conducted by psychologist Daryl Bem, and mentions an important basis for skepticism:

…[O]ver the past century dozens of such studies proclaiming statistically significant results have turned out to be methodologically flawed, subject to experimenter bias and nonreproducible.

Ben Goldacre, in his latest "Bad Science" column, departs from his usual medical beat to point out that the study has already failed an attempt to reproduce its results. However, the journal that ran the original study refused to publish the subsequent failed replication, on the grounds that it never publishes attempts to replicate other studies! If this is its genuine policy, and not an ad hoc excuse for rejecting the failed attempt, it strikes me as an extremely poor one.

The history of parapsychology, which is littered with unreproduced studies, shows why replication is a vital part of scientific method. An unreplicated study is worthless except as a guide to future research, so no one should take this study seriously unless and until it's reproduced.

Another problem that Goldacre discusses is publication bias:

…[T]hese positive results may have happened purely by chance, against a backdrop of negative results that never reached the light of day. Researchers and academic journals, just like newspaper journalists, are more likely to publish eye-catching positive results.

In other words, we don't know how many similar studies were done that failed to find statistically significant results and ended up in the researcher's file drawer. Given that the confidence level for statistical significance in scientific studies is usually set at 95%, this means that we can expect one in twenty studies to show significant results just by chance. If there are twenty or more studies filed away, then Bem's may just be the lucky one.

Goldacre also mentions a related problem:

We know that even if you analyse one study's results in lots of different ways, you increase the likelihood of getting a positive finding purely by chance.

This is a description of the multiple comparisons fallacy, which is the main error Nicolas Gauvrit discusses in his critique of the study. According to Gauvrit, once one corrects for multiple comparisons, Bem's results are no longer statistically significant.

According to Shermer, in one of the tests in which the subjects had a 50% chance of choosing the curtain behind which an erotic image would appear, they chose the correct curtain 53% of the time. This effect is only slightly better than chance, and would seem to show that precognition is very weak or unreliable. Thus, the study displays one symptom of "pathological" science described by Irving Langmuir:

The effect is of a magnitude that remains close to the limit of detectability; or, many measurements are necessary because of the very low statistical significance of the results. … Now the trouble with that is this. There is a habit with most people, that when measurements of low significance are taken they find means of rejecting data. They are right at the threshold value and there are many reasons why you can discard data. … If things were doubtful at all, why they would discard them or not discard them depending on whether or not they fit the theory.

Even if this didn't happen in Bem's study, whatever did happen only had to do so 3% of the time. If the effect were only larger, we could have greater confidence that something interesting really happened, but a 3% effect could be a lot of things other than precognition.

Sources:

Note: The remark used as a title of this entry is usually attributed to Yogi Berra, but is sometimes attributed to Niels Bohr of all people, probably incorrectly in both cases.


April 20th, 2011 (Permalink)

Taxing Doublespeak

If you drive a car, I'll tax the street
If you try to sit, I'll tax your seat
If you get too cold, I'll tax the heat
If you take a walk, I'll tax your feet
'Cause I'm the taxman…

Now, my advice for those who die
Declare the pennies on your eyes
'Cause I'm the taxman
Yeah, I'm the taxman
And you're working for no one but me

―George Harrison, "Taxman"

The prospect of a tax increase is a big occasion for political doublespeak. Few people look forward to a tax hike, at least if it's their taxes going up. As a result, politicians are always searching for linguistic ways to soften the blow, the best known of which was the Reagan administration's euphemism "revenue enhancement". In his speech of a week ago on the deficit, President Obama―or, more likely, one of his speechwriters―coined a new one:

The fourth step in our approach is to reduce spending in the tax code. In December, I agreed to extend the tax cuts for the wealthiest Americans because it was the only way I could prevent a tax hike on middle-class Americans. But we cannot afford $1 trillion worth of tax cuts for every millionaire and billionaire in our society. And I refuse to renew them again. … This is my approach to reduce the deficit…. It calls for tax reform to cut about $1 trillion in spending from the tax code.

In other words, the fourth step in Obama's plan to reduce the deficit is to allow some or all of Bush's tax cuts to expire. This is equivalent to a tax increase, though Obama says it is "to reduce spending in the tax code". There are, of course, two mutually-exclusive ways to lower a deficit: reduce spending or increase revenue. Raising taxes will no doubt increase revenue, and thereby contribute to a lower deficit, but it's not a spending reduction unless you think that the government not taxing people is thereby "spending" the money not taxed away. This would make sense only if the government in effect owns all the money in the country so that allowing people to keep their income is, thus, a type of spending.

This is a remarkable piece of doublespeak that makes "revenue enhancement" seem honest by comparison, for raising taxes does indeed enhance revenue. It just doesn't cut spending. The earlier phrase simply attempted to hide the unpleasant fact of higher taxes behind an unfamiliar phrase made up of long words, whereas the new one actually tries to convert the politically unpalatable tax hike into a more acceptable reduction of spending "in the tax code".

If new taxes are on the table, I'm sure that a tax on doublespeak would raise some revenue!

Source: "Text of Obama Speech on the Deficit", The Wall Street Journal, 4/13/2011


April 9th, 2011 (Permalink)

Bad Journalism

Check out Ben Goldacre's latest "Bad Science" column:

From 2006 to 2010 there was a 43% increase in number of prescriptions for the SSRI class of antidepressants. Does that mean more people are depressed in the recession?

At least the journalists who reported on this fact jumped to the conclusion that the recession caused the depression. Back to Goldacre:

…Iím not expecting journalists to go to academic research databases to conduct large complex descriptive studies. But if they are going to engage in primary research, and make dramatic causal claims―as they have done in this story―to the nation, I donít think itís too much to ask that they familiarise themselves with proper work thatís already been done, and consider alternative explanations for the numbers theyíve found.

Read the whole thing.

Source: Ben Goldacre, "When journalists do primary research", Bad Science, 4/9/2011


April 3rd, 2011 (Permalink)

Headline

Academics to dissect Bob Dylan at NY conference

They should at least wait until he's dead.


April 1st, 2011 (Permalink)

The Third Puzzle of the Absent-Minded Professors

For a third conference, which took place in early spring, the same four absent-minded professors (see the Resources, below) decided not to wear hats so that there could be no further mix-ups. However, it was still coat weather and―of course―each of them as they left managed to grab the coat of another one of the four.

Based on the appearance of the coats, we can assume the following:

  1. Either Professor Anderson took Professor Church's coat or Professor Belknap took Anderson's coat.
  2. If Anderson did not take Church's coat then Church took Belknap's.
  3. It's not true that both Anderson took Belknap's coat and Church did not take it.
  4. Anderson did not take Belknap's coat.
  5. If Church did not take Professor Davidson's coat then Belknap took Anderson's.

Can you determine who took Professor Davidson's coat?

Solution

Resources:

  1. The Puzzle of the Absent-Minded Professors, 2/4/2011
  2. The Second Puzzle of the Absent-Minded Professors, 3/5/2011

Solution to the Third Puzzle of the Absent-Minded Professors: Church took Davidson's coat.

Here are the steps leading to that solution. The reasons for each step are supplied in parentheses. Let's abbreviate the four professors' names as "A", "B", "C", and "D".

  1. C did not take B's coat. (From clues 3 and 4)
  2. If A took C's coat then C didn't take B's. (Clue 2)
  3. A took C's coat. (From the previous two steps.)
  4. B did not take A's coat. (By the previous step and clue 1)
  5. If B took A's coat then C did not take D's coat. (Clue 2)
  6. C took D's coat. (By the previous two steps)

Update (4/2/2011): In case you haven't already figured it out, the above puzzle was an April Fool's Day trick. The puzzle is unsolvable in that there is insufficient information to determine who took Davidson's coat. The real puzzle is to spot the fallacies in the above "proof" of the phony solution, for each step in the proof commits some fallacy. If you want to solve it yourself, go and do so before looking at the real solution below.

Real Solution


Real Solution to the Third Puzzle of the Absent-Minded Professors:

  1. Denying a Conjunct
  2. Improper Transposition
  3. Affirming the Consequent
  4. Affirming a Disjunct
  5. Commutation of Conditionals
  6. Denying the Antecedent

Second Update (4/2/2011): I've revised the puzzle to eliminate a pointless repetition in the fallacious "proof" of the bogus solution.

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