Patterico's Pontifications

5/8/2008

The L.A. Times’s Errors in Its Piece on DNA and Cold Hits

Filed under: Crime,Dog Trainer,General — Patterico @ 11:10 pm

I have sent the following e-mail to the authors of that L.A. Times piece on DNA and cold hits:

Mr. Felch and Ms. Dolan,

I believe your recent front-page article on DNA cold case statistics misstated the meaning of the math you discuss.

Your article said:

Jurors were not told, however, the statistic that leading scientists consider the most significant: the probability that the database search had hit upon an innocent person.

In Puckett’s case, it was 1 in 3.

The 1-in-3 number does not pertain to the probability that the database search had hit upon an innocent person. Rather, the 1-in-3 number pertains to the probability that a database search will result in a single match — whether that match is to an innocent person or a guilty one.

If we ignore the existence of independent evidence of Puckett’s guilt, the statistical chance Puckett is innocent depends in part on the probability that the database contains the guilty party. Your article gives no information on what this probability is (although the fact that the database consists of California-based felons suggests that the chances are better than one would find in a purely random database). Without knowing the probability that the database contains the guilty party, you can’t conclude that the 1-in-3 figure accurately represents the chances Puckett is innocent. Your article confuses two distinct concepts and requires correction.

You state:

In every cold hit case, the panels advised, police and prosecutors should multiply the Random Match Probability (1 in 1.1 million in Puckett’s case) by the number of profiles in the database (338,000). That’s the same as dividing 1.1 million by 338,000.

Actually, you have that upside down. Multiplying (1 in 1.1 million) by 338,000 is the same as dividing 338,000 by 1.1 million — not dividing 1.1 million by 338,000.

Your article continues:

For Puckett, the result was dramatic: a 1-in-3 chance that the search would link an innocent person to the crime.

Again, this is wrong. There is a 1-in-3 chance that the search would link someone to the crime. Whether that person is innocent or not depends on the likelihood that the database contains the guilty party (as well as the quality of other evidence tying that defendant to the crime).

I am not the only person saying this. A similar point was made by Eugene Volokh in this post. And I made the point in more detail in this blog post of mine.

I think the paper owes readers at least two corrections — one of the 1-in-3 statistic, and one on the upside-down division. Given the prominence of the error on the 1-in-3 statistic, which appeared on the front page of the Sunday paper, I hope your paper will make an effort to give this correction the prominence it deserves.

cc: Readers’ Representative

I’ll let you know what I hear in response.

P.S. When I say “Rather, the 1-in-3 number pertains to the probability that a database search will result in a single match — whether that match is to an innocent person or a guilty one.” I meant to express this concept: “Rather, the 1-in-3 number pertains to the probability that a database search will result in a single match, period. If we get a single match, we won’t know whether it was to an innocent person or a guilty person without learning more.” In other words, without prior knowledge of the likelihood that the database has the guilty person, all we know is the chance of a hit — not the chance that a single hit has come back to an innocent person.

P.P.S. I just changed the last phrase from “not the chance of a hit to an innocent person” to “not the chance that a single hit has come back to an innocent person.” That more accurately expresses what I was trying to say.

Expressing statistical concepts in accurate English is like walking a tightrope.

California Democrats Propose More Taxes to Cure Budget Shortfall

Filed under: Economics,Politics — DRJ @ 10:43 pm

[Guest post by DRJ]

Get ready, Californians.

Democrats in the California Legislature plan to solve the $20B budget shortfall by taxing your six-packs ($1.80 per pack), iTune downloads ($0.08 per download), and plastic grocery bags ($0.25 each). Other proposals include increased taxes on porn magazines, sex toys, yachts, and gas-guzzling vehicles.

At least they aren’t taxing California blogs. Yet.

— DRJ

Let the Swift-Boating Begin

Filed under: 2008 Election — DRJ @ 8:41 pm

[Guest post by DRJ]

Many Democrats use the term Swift-boating to mean an unfair attack against a candidate. By that standard, alert Instapundit reader Scott Slater provides an early example of Swift-boating by the Democrats:

“Dear Glenn,

Got the 2008 Democratic Presidential Survey in the mail today.

Question #7 – “Do you believe that John McCain’s pledge to keep troops in Iraq for another 100 years will be a liability in the General Election?”

I answered “No. He didn’t say that. You are smearing him.”

Question #11 asks “How likely do you think it is that John McCain and his Republican allies will launch a “Swift Boat” style smear campaign against our presidential nominee?”

I checked “Not Likely, but I noticed you have (see question 7).”

It doesn’t sound like Scott sent in a contribution with his response.

— DRJ

Code Pink is Bewitched

Filed under: Politics,War — DRJ @ 7:41 pm

[Guest post by DRJ]

Apparently the special parking and permits granted to the Bay Area Code Pink to protest the Marine Corp recruiting center in Berkeley hasn’t done the trick. Now Code Pink is calling on area witches, crones and sirens to bewitch the Marines:

“Friday, May 9th: Witches, Crones, Sirens: perform rituals of leaving, cast a spell of peace and love over the station, rendering nil the recruiting of our youth to become fodder for this occupation of Iraq.”

Catherine Moy at Move America Forward broke the story and adds this detail:

“This should be no surprise. One of Code Pink’s mamas is Miriam Simos, a bisexual feminist witch living in Berkeley who goes by the name “Starhawk.” I’m sure Starhawk and the rest of the witches of Code Pink will work up a real witches’ brew of hate for our Marines.”

I hope Code Pink ends up with three witches. The symbolism would be perfect.

— DRJ

Illegal Immigration is in the News in Idaho

Filed under: Crime,Immigration — DRJ @ 7:16 pm

[Guest post by DRJ]

A 10-year-old Idaho girl has given birth after being raped, allegedly by a 37-year-old illegal immigrant.

The accused is in the Fremont County, Idaho, Jail on other rape charges.

— DRJ

Al Qaeda in Iraq Leader Captured in Mosul (Updated)

Filed under: Terrorism,War — DRJ @ 3:19 pm

[Guest post by DRJ]

Iraqi sources report that al Qaeda in Iraq leader Abu Ayyub al-Masri has been captured in Mosul. If this report is correct, al-Masri almost made it to his 2-year anniversary as commander. He took over al Qaeda in Iraq after Abu Musab al-Zarqawi was killed June 7, 2006 in a U.S. airstrike northeast of Baghdad.

As discussed in this post, al-Masri’s top two aides were killed in October 2007, including one who was in charge of foreign suicide bombers.

Apparently al-Masri is in Iraqi custody. Imagine the information al-Masri could share regarding plans for suicide attacks and the identities of possible suicide bombers. If he is turned over to the Americans, what interrogation techniques should be allowed to get information from al-Masri about planned attacks and personnel?

UPDATE: Once again, it looks like reports of al-Masri’s death or capture are untrue or, at least, premature.

— DRJ

Summertime Politics

Filed under: 2008 Election — DRJ @ 12:47 pm

[Guest post by DRJ]

Clinton campaign chairman Terry McAuliffe predicted that Hillary Clinton will end her campaign in early June if she’s not the party’s nominee. His words are apparently intended to reassure superdelegates and party leaders that Hillary will not hurt party unity by unduly continuing her candidacy.

Meanwhile, Hillary Clinton is focusing on electoral votes and electability:

“The delegate math may be complicated, but the electoral math is easy,” Clinton said, arguing that presumptive Republican nominee John McCain is a “formidable opponent” and that she has won more “swing states” — such as Ohio, New Jersey and Pennsylvania — than Obama.”

And Barack Obama is lobbying party leaders and superdelegates in Washington DC. He met briefly with House Speaker Nancy Pelosi of San Francisco and Majority Leader Steny Hoyer of Maryland as well as some Clinton supporters, Democratic Reps. Ellen O. Tauscher of Alamo and Alcee Hastings of Florida.

Last night Karl Rove said that if he were advising Obama, he would recommend that Obama spend most of the summer in Washington DC pursuing bipartisan legislation that supports his claim he’s a uniter. Rove’s point was there is no evidence Obama is the bipartisan he claims to be.

However, after reading Tom Maguire’s post on Obama The Answer Man, I doubt Obama is interested in any group projects this summer.

— DRJ


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