May 2008 archive

Bayes’ theorem is useful in evaluating the result of drug tests. Suppose a certain drug test is 99% sensitive and 99% specific, that is, the test will correctly identify a drug user as testing positive 99% of the time, and will correctly identify a non-user as testing negative 99% of the time. This would seem to be a relatively accurate test, but Bayes’ theorem will reveal a potential flaw. Let’s assume a corporation decides to test its employees for opium use, and 0.5% of the employees use the drug. We want to know the probability that, given a positive drug test, an employee is actually a drug user. Let “D” be the event of being a drug user and “N” indicate being a non-user. Let “+” be the event of a positive drug test. We need to know the following:

   * P(D), or the probability that the employee is a drug user, regardless of any other information. This is 0.005, since 0.5% of the employees are drug users. This is the prior probability of D.

   * P(N), or the probability that the employee is not a drug user. This is 1 ? P(D), or 0.995.

   * P(+|D), or the probability that the test is positive, given that the employee is a drug user. This is 0.99, since the test is 99% accurate.

   * P(+|N), or the probability that the test is positive, given that the employee is not a drug user. This is 0.01, since the test will produce a false positive for 1% of non-users.

   * P(+), or the probability of a positive test event, regardless of other information. This is 0.0149 or 1.49%, which is found by adding the probability that the test will produce a true positive result in the event of drug use (= 99% x 0.5% = 0.495%) plus the probability that the test will produce a false positive in the event of non-drug use (= 1% x 99.5% = 0.995%). This is the prior probability of +.

Given this information, we can compute the posterior probability P(D|+) of an employee who tested positive actually being a drug user:

P(D|+)  = (0.99 x 0.005)/(0.99 x 0.005)+(0.01 x 0.005)

P(D|+)  = 0.3322

Despite the high accuracy of the test, the probability that an employee who tested positive actually did use drugs is only about 33%, so it is actually more likely that the employee is not a drug user. The rarer the condition for which we are testing, the greater the percentage of positive tests that will be false positives.

1. The Washington Post reports that FBI reports Of detainee abuse were ignored by the White House.

   Complaints by FBI agents about abusive interrogation tactics at Guantanamo Bay, Cuba, and other U.S. military sites reached the National Security Council but prompted no effort to curb questioning that the agents considered ineffective and possibly illegal, according to an internal audit released yesterday.

   Reports that Guantanamo detainees were being subjected to extreme temperatures, religious abuses and nude interrogation were conveyed at White House meetings of senior officials in 2003, yet these questionable tactics remained in use, a lengthy report by the Justice Department’s inspector general concluded.

   In one instance, colleagues of then-Attorney General John D. Ashcroft reported that he personally aired concerns about Defense Department strategy toward a particular detainee with Condoleezza Rice, then the national security adviser, while other Justice managers shared similar fears with the council’s legal adviser in November 2003, the report said.

   From the report via TPM Muckraker, an inventory of the abuse and torture reported by the FBI agents to the Justice Department Inspector General. Of the 450 interviewed, “nearly half reported witnessing or hearing about ‘rough or aggressive treatment of detainees, primarily by military investigators.'”

Four at Four continues with stories about big oil, the environment, and tornadoes.

(h/t to GreyHawk for pointing to this story. GH’s post at epluribus media.)

Yes, the FBI kept a “War Crimes” file about GTMO. So reports the NY Times in  Report Details Dissent on Guantánamo Tactics:

WASHINGTON – In 2002, as evidence of prisoner mistreatment at Guantánamo Bay began to mount, Federal Bureau of Investigation agents at the base created a “war crimes file” to document accusations against American military personnel, but were eventually ordered to close down the file, a Justice Department report revealed Tuesday.

Ordered closed down by whom exactly?

John McCain is having some serious difficulty getting the big Republican doners (you know those guys; the 1 percenters with all the money) to give money to his campaign for the Republican Presidential nominee.

It has gotten so bad and his funding is trailing both of the Democratic Presidential Candidates by so much that McCain is planning to tap into the Republican National Committee to help him fund his campaign.

From The New York Times:

Pivoting toward the general election, Senator Barack Obama is turning again to his history-making fund-raising machine, which helped to anoint him as a contender against Senator Hillary Rodham Clinton and then became a potent weapon in their battle for the Democratic nomination.

To confront the Obama juggernaut, Senator John McCain, whose fund-raising has badly trailed that of his Democratic counterparts, is leaning on the Republican National Committee. Mr. McCain’s efforts to raise money suffered a blow this weekend when a key fund-raiser, Tom Loeffler, resigned because of a new campaign policy on conflicts of interest.

UN Secretary General Ban Ki-Moon is en route to Myanmar today, but already his presence in the region seems to have had an affect:

“We have received government permission to operate nine WFP (World Food Program) helicopters, which will allow us to reach areas that have so far been largely inaccessible,” Ban told reporters in New York on Tuesday before departing for Southeast Asia. His announcement was not immediately confirmed by officials in Myanmar.

“I believe further similar moves will follow, including expediting the visas of (foreign) relief workers seeking to enter the country,” Ban said, warning that relief efforts to save survivors of the May 2-3 Cyclone Nargis had reached a “critical moment.”

“We have a functioning relief program in place but so far have been able to reach only 25 percent of Myanmar’s people in need,” he said.

link: http://ap.google.com/article/A…

Progress can’t come too soon, as cyclone victims, desperate for food, beg by the side of the road:

What makes a President?

This is an attempt, by using the Eight Stages of Genocide by Gregory H. Stanton, to show how climate change is a human rights issue in our own backyard.