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Smaller Sample Size, Please

This is an interesting tidbit from David Lykken’s “Professional Autobiography” that was once available on the webpage of the U of MN’s Psych department website:

When I was a graduate student circa 1950, I had a job for several months in the Student Counseling Bureau analyzing the returns from a “After High School What?” survey that one of the counseling faculty had administered to 57,000 seniors in Minnesota high schools. In the basement of Eddy Hall, I would run boxes of IBM cards, each bearing the responses of one student, through the IBM sorting machine. A few years later, when I was on the faculty myself, Paul Meehl and I used those data for our unpublished “crud factor” study in which we showed that, in psychology, everything is related to everything else, at least a little bit. We cross-tabulated all possible pairs of 15 categorical variables on the questionnaire and computed Chi-square values. All 105 Chisquares were statistically significant and 96% of them at p less than 10-6. Thus, we found that a majority (52%) of Episcopalians “like school” while only a minority (47%) of Lutherans do. Fewer ALC Lutherans than Missouri Synod Lutherans play a musical instrument.

What this silly-sounding study implies is that Group A is bound to differ from Group B on Variable X so that, if your theory predicts that A > B, you have about a 50:50 chance of confirming that prediction empiricallyat least if you have a large enough sampleeven if your theory is dead wrong.

Meehl used these data as illustrations in a 1967 paper in Philosophy of Science. He pointed out that the physical sciences, whose theories are strong enough to permit point predictions (Group A will average 125% of Group B’s score, rather than merely A > B), use significance tests in a way that is obverse to the way they are used in the soft sciences. Psychologists say, e.g., that X and Y will be correlated positively and, if that much proves true, then we try to “reject the null hypothesis” by showing that the correlation is so far above the zero or null point, that there is less than one chance in 20 (or more) that the true value of the correlation (which our obtained value estimates) could be as low as zero.

One unhappy consequence of this way of proceeding is that our conclusions become more suspect as our experiment gets better! If we use good, reliable measures of X and Y, then we are more likely to detect the (almost inevitable) correlation between them, and the larger our sample, the more likely it is that this detected correlation will be statistically significant, i.e., have a small enough sampling error and be far enough from zero to believe it really is not zero. A cheap, crappy experiment with poor measures and a small sample that can report a statistically significant result is therefore regarded as more persuasive than a good, big study!

I’ve added some bolding for emphasis. This form of data-mining isn’t really discussed anywhere, from what I can tell, in the popular press or even in academic settings.

Professor Lykken’s autobiography is worth a read.

DB Cooper: J’accuse

Originally, I was going to save this reveal for a book, but after thinking it over I decided to fully present my case on the blog. This will come in the form of several posts over the next few months. So here it goes…

When first reading through the Kaye evidence, I figured it would be an easy matter to eliminate all the publicly known suspects. I figured I’d find a bunch of dead ends, and that would be that. I could move on with nothing more to add to the Cooper literature.

I set about doing just that.

Well, Cooper Curse. The first “obviously not Cooper” suspect ends up matching with the Kaye evidence, and my plans on extricating myself from the case is out the window. Cooper Curse meets Cooper Vortex.

Who is this suspect? “Dan LeClair”, the pseudonym for an anonymous suspect presented in a book by a long-deceased author about a much-lampooned love story involving a lonely divorcee and D.B. Cooper. Somehow, this much-maligned mystery man has ended up being the strongest candidate not fully vetted with a proper investigation.

Max Gunther, best known as a financial writer (Zurich Axioms) wrote a book called “D.B. Cooper: What Really Happened” in the mid-80’s. In it, he describes being contacted by someone claiming to be D.B. Cooper shortly after the hijacking. This individual later flaked, and Gunther forgot about the whole affair for more than a decade.

However, he was later contacted by a woman claiming to know the real Dan Cooper who said the mysterious hijacker had recently passed away. After a few letter exchanges, Gunther interviewed the woman six times over the phone for about an hour a session. Then she, too, flaked. Gunther was able to put together the story into the form of a book, and it was immediately considered a hoax by the FBI.

Later, Jo Weber read the book, and it somehow convinced her that her former lover, Duane weber, was Dan Cooper. Over the course of a decade, or so, on the original Cooper thread on the DropZone website, Weber presented her case and was excoriated for her ambiguous statements and shifting positions. And rightly so. But along with attacking Weber, the forum members also tore down the Gunther book, almost solely by association.

To my knowledge, no one has fully investigated Gunther’s candidate.

I’ll be looking more closely at the book and examining all that can be examined over the next series of posts.

Here, I’ll quickly present the reasons why I think “Dan LeClair” deserves a closer look. Of most interest are those items that match with revelations about the case that didn’t become public, or where even discovered, until long after the book was published:

1) LeClair worked in the industrial chemical industry for more than a decade, as a salesman and manager, and possibly an executive. This coincides with the most important evidence found by Tom Kaye: the presence of unalloyed titanium on Cooper’s tie.

Max Gunther died in the late 90’s, and he would not have known how important Cooper’s actual profession would be in identifying a suspect.

2) “LeClair” absconded just before the hijacking. He told his wife he was going on a trip for work, and he told his employers he was going on vacation. He left his home wearing his work suit. This was the suit he later wore on the airplane. Gunther would not have known how important it was that Cooper was wearing his work suit and not something cheap purchased at a thrift shop.

3) “LeClair” was French-Canadian. There were several clues from the hijacking that suggested Cooper was Canadian (mostly phrases he used).

4) LeClair was a paratrooper, but not a skydiver. Gunther may have picked this up from the FBI, or not, but it is generally recognized that Cooper was not a skydiver.

5) LeClair read male action-adventure literature. Thus he might have been familiar with the comic “Dan Cooper” which was a French-only adventure comic produced from the late fifties to the hijacking.

6) As a Canadian who probably had to travel a lot, he would be more likely to use the phrase “negotiable currency” than your typical American. (And as a frequent traveler, he would have been familiar with much of commercial aviation procedures, equipment and lingo)

7) The story matches what we know from parachuting data (something I still haven’t published here yet, I’m working on it): Pulled ripcord, injured but mobile on the ground. Also, the drop zone isn’t moved either, which is common in most self-confessed Cooper stories.

I’ll be hitting each of these bullet points in-depth, as well as looking at other details from the book, answering objections, and I might even go through the other popular suspects. This is only an introduction.

DB Cooper: What I think Happened

When I first started looking into this case, my opinion was that whoever DB Cooper was, he was not one of the suspects regularly talked about online or on TV. So I took the available evidence, read as much as I could, and created a rough overview of all the evidence. I also wanted to look at what might have happened to Cooper after he left the 727 with his bag of money and a parachute. I outlined everything I thought happened, within a reasonable level of confidence. [I posted an abbreviated version of this on the DB Cooper Forum.]

Since starting out, I have found the case to be much more complex than I first thought. I have also found out that, like others, I do have a favorite Cooper suspect. However, I feel it would still be valuable to go over my initial conclusions, with a revision or two based on exchanges with other Cooper researchers on the forum.

Who was Dan Cooper?

First and foremost, Cooper was not a criminal before hijacking the airplane. The FBI had Cooper’s fingerprints (almost assuredly), and had years to look into suspects with a known criminal history. When Himmelsbach says Cooper was “an old con,” he’s making a fundamental error. In all probability, the hijacking was Cooper’s first crime.

From Tom Kaye’s analysis of the tie, we get a different picture of Dan Cooper. He was educated, worked as an engineer or manager. He could have even been a metallurgist. Cooper possibly worked at Boeing on the 727, which would explain some of his knowledge of the airplane’s rear stairs and flap settings. The timing of the hijacking is also of interest, as it took place just after the supersonic transport (SST) program lost its federal funding. Lots of workers lost their jobs.

Since the tie did not have any wild pollen on it, we don’t know where exactly Cooper lived. The FBI took a long look at Boeing, so Cooper was not a current or recently released employee there. Parts of the SST program were being worked on all over the country, so we again can’t pinpoint Cooper’s hometown. We do know, based on the knowledge he displayed during the hijacking, that Cooper lived in the SeaTac area at some point in his life, probably before leaving Boeing and pursuing a job in aviation at some other company.

Cooper was ex-military. He was either a paratrooper or a loadmaster. He was literate, well-spoken, and level-headed. He was a casual smoker and a light drinker. He was taking some form of prescription medication, probably for heart disease. Since he asked for “negotiable currency” and his name “Dan Cooper” might have come from a French-language comic book hero, Cooper could have been born and raised a French-Canadian before emigrating. Cooper was either a lifelong bachelor or recently divorced (he made his jump the day before Thanksgiving, so it’s unlikely he was worried about needing to be somewhere the next day.) He need not have been a loner, as Cooper remained quite calm and conversed for hours with a complete stranger, showing a high degree of social skill.

Much has been made of Cooper’s “olive” skin tone. It could mean he was of Hispanic descent, or he might have been an avid outdoorsmen or golfer. Hang around a golf course in late August and early September, plenty of guys sport a deep tan. I mention golf because it’s a universal business sport, and Cooper was a white collar guy.

What of the Jump?

Having now spent several months reviewing hundreds of combat jumps made by RAF airmen during nighttime missions in WWII, I believe I have a solid dataset to make some reasonable inferences about what happened to Cooper between the 727 aftstairs and the ground [I intend to publish these findings at a future date].

To put it simply: If an airman was able to get out of his stricken craft in a conscious state and with enough altitude to deploy his parachute, there was an almost 100% pull rate. Some of the interesting jumps I’ve read about include: an RAF airmen who had to attach his parachute in freefall, in the dark; another who had a 20mm cannon round sticking out of his thigh; a successful jump with a parachute clipped to a harness on only one d-ring; not to mention dozens of guys thrown from exploding airplanes. Taken together, we can conclude that even inexperienced jumpers find a way to deploy their parachutes.

So Cooper pulled the ripcord. It would have been a hard opening for Cooper. He might have lost his shoes (reported to be slip-on loafers) and I think he also lost the bag of money. Paracord is difficult to tie into knots, and the amount of force involved in a parachute opening is not kind to improvised anything. At least one of Cooper’s copycats lost their money during the jump, and most of them put more planning into their capers.

Cooper pulled the ripcord early, likely as soon as he stabilized into freefall (it was dark, and Cooper had no way to judge altitude). So Cooper was pushed by the wind for a very long time and might have traveled up to seven miles (but more likely around 4 miles). If the published FBI flight path is accurate, he landed a few miles east of Battleground, WA. This was mostly farming country, and pretty flat.

It would have been a blind landing (no moon light, totally dark) with a fifteen mile per hour wind. Try jumping from the top of a car moving 15mph with your eyes closed. It would hurt. Paratroopers are taught how to land in ways that minimize injury, but this would still be a tough landing. There’s a very good chance he was injured, a broken ankle or a fractured spine. About half of RAF airmen were injured in their jumps, but almost all of them were mobile and had the ability to evade capture for a little while after their jumps. So Cooper was probably capable of moving away from his landing zone. In the dark, with at least ten hours before an air search would be able to find him, Cooper would have plenty of time to make his escape.

His Escape:

Landing in a field somewhere, Cooper would move quickly to either a road or shelter. He probably buried his gear or just tossed it somewhere into deep brush. It’s possible he was able to get a ride from someone, likely telling a story about a car accident or something. Since the FBI checked all the hotels and motels right after the hijacking, Cooper probably either stayed with his helpers for the night, or was able to get transportation out of the area.

What about the manhunt? What about the roadblocks? Cooper landed farther south than the FBI thought. The actual manhunt was very pathetic, and was in the wrong area. If Cooper was able to go south into Vancouver, or hitch a ride east, there were no roadblocks to worry about. If Cooper was living in Portland, it’s completely possible he got a ride all the way home.

Cooper paid for his plane ticket with a fresh $20 bill, and later used another $20 to pay for a drink on the airplane, getting about $18 in change. So he had money on him. If I were planning this caper, I would have plenty of cash on me. So even if Cooper lost the ransom money, he was not without resources. If anyone did help Cooper and later came to be suspicious of the shoe-less and injured man they drove to Portland, they might have been afraid to talk about it, lest they be arrested as accomplices. Chances are, Cooper’s story stuck and they never even considered the stranger they met 12 miles south of the FBI search zone to be anything other than the world’s unluckiest dude.

The Money:

Three bundles of money were found on a sandbar about twenty miles away from the drop zone, and there’s no reasonable way to explain how the money traveled so far with rubber bands still attached. The general conclusion I draw from everything I’ve read about the Tena Bar money find is that it is indecipherable. So far, no explanation presented comes close to explaining the details of how the money got there.

If Cooper lost the money in the jump, like I suggest above, then someone else must have found the money. Greed would keep the find secret. While there were rewards for helping to apprehend Cooper, they did not add up to the $200,000 in the bag. Even after the statute of limitations had expired, the people who found the money would still owe taxes on their windfall. Not too shocking, then, that these people never talked.

The FBI revealed a couple of years later that all the serial numbers on the bills had been recorded, and they gave the impression that the money was therefore unspendable. If someone had found the money and was given the impression they would go to jail (or owe a ton of money to the IRS) if caught with it, I’m sure they would have disposed of it. Like by throwing it into a river. Or maybe they buried it near the Columbia. Some of the forum members have suggested the money looks like it was burned. It’s possible someone tried to completely destroy the bills by throwing them in a fire, not noticing the several bundles that weren’t completely burned.

These are all just guesses, and details surrounding the Tena Bar find are among the most speculative to be found in this case. Regardless, Cooper lost some or all of the money, and some of it ended up at Tena Bar. Anyone who might have found the money would have little incentive to talk about it, and we’re all waiting on some deathbed confessions to move the case along in this area.

And The Rest

Cooper, injured and broke, probably watched the news non-stop for the next couple of weeks. After making his escape, he might have taken all his available resources and left the area for good. Or, he could have stayed and returned to his regular life. He did his crime on a four day weekend, so his coworkers would have assumed he was with family. He comes in on Monday with a new tie, new shoes, and maybe a limp from a “car accident.”

He makes no large purchases. His lifestyle doesn’t change. There’s no way to connect him to the crime. For whatever reason, the artist sketch doesn’t quite look like him (much like the Unabomber case) and there’s simply no one who can put him on that airplane. Besides, Dan Cooper was a white collar guy, a regular Joe Doakes, he was boring. No one would believe the metallurgist on the shop floor was jumping out of airplanes. And above all, Cooper doesn’t talk to anyone. Ever.

Long suffering from a chronic medical condition, Cooper dies sometime before Unsolved Mysteries airs its DB Cooper episode (October, 1988), the one with the new and improved artist sketch. Some of his coworkers mourn his passing, maybe he had a few close friends. A nephew shows up to his funeral. His ex-wife skips the whole affair. It turns out to be the greatest adventure never told.

Interesting Abstract

Aspartame consumption is implicated in the development of obesity and metabolic disease despite the intention of limiting caloric intake. The mechanisms responsible for this association remain unclear, but may involve circulating metabolites and the gut microbiota. Aims were to examine the impact of chronic low-dose aspartame consumption on anthropometric, metabolic and microbial parameters in a diet-induced obese model. Male Sprague-Dawley rats were randomized into a standard chow diet (CH, 12% kcal fat) or high fat (HF, 60% kcal fat) and further into ad libitum water control (W) or low-dose aspartame (A, 5-7 mg/kg/d in drinking water) treatments for 8 week (n = 10-12 animals/treatment). Animals on aspartame consumed fewer calories, gained less weight and had a more favorable body composition when challenged with HF compared to animals consuming water. Despite this, aspartame elevated fasting glucose levels and an insulin tolerance test showed aspartame to impair insulin-stimulated glucose disposal in both CH and HF, independently of body composition. Fecal analysis of gut bacterial composition showed aspartame to increase total bacteria, the abundance of Enterobacteriaceae and Clostridium leptum. An interaction between HF and aspartame was also observed for Roseburia ssp wherein HF-A was higher than HF-W (P<0.05). Within HF, aspartame attenuated the typical HF-induced increase in the Firmicutes:Bacteroidetes ratio. Serum metabolomics analysis revealed aspartame to be rapidly metabolized and to be associated with elevations in the short chain fatty acid propionate, a bacterial end product and highly gluconeogenic substrate, potentially explaining its negative affects on insulin tolerance. How aspartame influences gut microbial composition and the implications of these changes on the development of metabolic disease require further investigation.

Low-dose aspartame consumption differentially affects gut microbiota-host metabolic interactions in the diet-induced obese rat.

Weekend Reading

Robot Nation:

…the workplace of today is not really that much different from the workplace of 100 years ago. Humans do almost all of the work today, just like they did in 1900. A restaurant today is nearly identical to a restaurant in 1900. An airport, hotel or amusement park today is nearly identical to any airport, hotel or amusement park seen decades ago. Humans do nearly everything today in the workplace, just like they always have. That’s because humans, unlike robots, can see, hear and understand language. Robots have never really competed with humans for real jobs because computers have never had the vision systems needed to drive cars, work in restaurants or deliver packages. All that will change very quickly by the middle of the 21st century. As CPU chips and memory systems finally reach parity with the human brain, and then surpass it, robots will be able to perform nearly any normal job that a human performs today.

A number of my friends have suggested the coming robotic/AI revolution will be similar to previous technological innovations, like the Ford factory line or the personal computer; implying that the worst case scenario is just obtuse Luddite thinking from the anti-technology crowd. I am not so sure.

Read the whole thing.

Wisconsin or Minnesota

A common meme among my liberal friends is that Governor Scott Walker has taken Wisconsin to the brink of disaster with his right-wing public sector union busting. And that billionaire 70’s star child Mark Dayton, who has raised taxes and spent a bunch of money and raised the minimum wage, has led a miracle of liberal utopianism in Minnesota.

What’s the reality? Well, I decided to take a look at the BLS to see how much truth there was to this meme. And I found the following graphs.

Without cheating, can you tell which of the below is Minnesota, and which is Wisconsin?



While it looks like the recession hit one state a lot harder than the other, the employment recoveries look very similar.

Because they are. Here is the graph from the Star Tribune that normalizes the job recoveries of “selected” Midwest states:

Midwest Job Growth Strib

While Minnesota is doing a little better than Wisconsin, it’s the real-world equivalent of a rounding error. The real Midwest miracle has been North Dakota.

DB Cooper Suspect Checklist

The Cooper Case has generated an endless crop of suspects, over a thousand individuals were investigated by the FBI. Now there are a dozen or so favorite suspects that are talked about on forums, in books and on the Cooper Wikipedia page. While there is some interesting circumstantial evidence for each of the suspects, no one has really created a checklist of necessary characteristics and details to really pin down if any of the suspects make any sense. At least, not from what I can find. (I would wager that the FBI had their own checklist at some point.) So I gave it a shot. Here is my list of features that any Cooper Suspect needs to address:

1) Parachute/Harness; Cooper was able to put on his parachute with relative ease. He checked the packing card on his chosen chute, and refused a note on how to use a parachute. Any Cooper suspect needs to have a background that adequately explains why they were so comfortable with the parachute harness, and how they knew to inspect the packing cards.

2) “Negotiable Currency“; Cooper at one point asked for “negotiable” currency, which is an odd thing for most Americans to say. Any Cooper suspect would have to be well-traveled or have above average financial knowledge, or be from Canada. He did not have a noticeable accent, which further limits the pool of suspects who would use this phrase.

3) Knowledge of the 727; Somehow, Cooper knew the flap settings on the 727, he knew there was no locking mechanism on the doors (where other airliners had locks on their aft stairs), he knew what the phones on the plane were called, and was familiar enough with flying to know you could submit a flight plan after takeoff. That’s too much knowledge to “luck” into.

4) Matches Physical Description; Cooper was definitely taller than one of the stewardesses. Probably around six feet. Middle age. He had a medium build, olive complexion and dark hair.

5) Reminiscent of Sketch; The FBI composite sketches are not perfect, but any Cooper candidate should be vaguely reminiscent of them.

6) Eyewitness affirmation; There are still several living witnesses to the hijacking. Two of the stewards and one passenger had extended contact with Cooper. They should be able to give a thumbs up or down on any suspect. [None of these living witnesses speaks openly about the case, so it will be impossible for amateur sleuths to get such affirmation.]

7) Knowledge of Sea-Tac area; Cooper could recognize Tacoma from the air, and he also knew the travel time between McChord Air Force Base and the SeaTac airport. While it’s possible Cooper could have gotten this information through intense planning and scouting, it’s more likely he already knew the area. He probably lived or worked in the area at some point in his life.

8) Unknown whereabouts during hijacking; Goes without saying, any Cooper suspect must have had an opportunity to commit the crime.

9) Smokes, preferably Raleigh Cigarettes; Cooper was at a minimum a casual smoker, a pack a day or less. He was probably not a heavy smoker. Tie evidence suggests he had been a smoker for a long time.

10) Dan Cooper reader; Some explanation for the Dan Cooper alias would be nice. Currently, the prevailing theory is Cooper had read the Franco-Belgian comic book series called “Dan Cooper.” An American GI could have encountered the comic while serving overseas as early as 1957. The comics were written in French, so that would make Cooper bi-lingual (though he had no accent in English). This is highly speculative, and as such is the least important item on the checklist. One of the anecdotes FBI agent Ralph Himmelsbach gives in his book Norjack is investigating a Cooper suspect, who was a jumper, had circumstantial evidence of involvement in the case, and his real name was “Dan Cooper.” Cooper could have gotten has alias from a phonebook. We don’t know.

In addition to the above checklist, there was evidence recently found on the tie that was probably left by Cooper on the airplane (though there is no way to prove the tie was his). Since the tie can’t be proven to have belonged to Cooper, and since there is a strong possibility of cross contamination, all the clues found on the tie should be considered speculative. (Tie evidence was collected and analyzed by Tom Kaye’s Cooper team.)

Tie Clues:

Clip-on tie user

The tie is a clip-on. As a general rule, people are either clip-on tie users or not. While it is completely possible someone who wears regular ties would use a clip-on tie (perhaps as a safety measure for a parachute jump) for a skyjacking, I tend to think Cooper was a regular clip-on tie user.

Pictures with similar tie clip

The tie clip found on the tie was a common design, sold for decades, so not a definitive test. However, the tie clip had been on the tie for a long time, in exactly the same spot, which would make photo-matching a suspect a possibility.

Titanium Particles

Pure titanium particles were found on the tie. An unusual thing in 1971, Cooper could have only been exposed to it at a few factories and chemical plants across the country. This means Cooper likely worked in those places, and as a tie wearer, he was likely a manager or an engineer.


Particles consistent with packing materials from prescription drugs were found on the tie, suggesting Cooper regularly took prescription medication for some condition leading up to the hijacking.

Partial DNA Match

Some DNA was found on the tie. I believe the tie is likely contaminated by being handled by numerous FBI agents after being collected (these were pre-DNA times). But, getting a match from a suspect to this DNA would disprove my theory and confirm a suspect.

Over the coming year, I hope to apply this checklist to all the existing Cooper suspects and see if any come close to matching the evidence.

Trouble in Pallettowne

Pallets are the most boring, every day thing… right?

The origin of the pallet is unknown. Rick LeBlanc and Stewart Richardson, co-authors of the indispensable Pallets: A North American Perspective, believe that an early prototype was used to aid in the stacking of wooden barrels in a warehouse in Louisbourg, Nova Scotia, in the mid-eighteenth century.4 But the story becomes more certain only in the early twentieth century, when a machine resembling a heavy-duty golf cart appeared on the American warehouse scene. It was called a “lift truck,” and it had a large iron spatula protruding from its front.

Various proto-pallets, or “skids,” were used in concert with these early lift trucks. Some of the skids were wooden; some were metal; some had little iron legs, which allowed clearance for the spatula. Eventually, the iron legs faded into history—too extravagant—and were replaced by a pair of wooden support beams, called “stringers,” which gave the skid about six inches of height. Then the spatula mutated into a two-tined fork, and the skid, responding in kind, grew a third stringer along its dorsal spine. Around 1925, the skid gained a set of bottom deck boards, below the three stringers, and with this, the pallet had achieved its modern form. Functionally, this new bottom deck stabilized the pallet, which prevented stacks of goods from crashing down in the warehouse. Aesthetically, the effect was striking: the pallet had become a thing, alive and whole.

Although the technology was in place by the mid-1920s, pallets didn’t see widespread adoption until World War II, when the challenge of keeping eight million G.I.s supplied—“the most enormous single task of distribution ever accomplished anywhere,” according to one historian—gave new urgency to the science of materials handling. During the summer of 1941, at Fort Wayne, Indiana, the army staged a field test of various materials-handling contraptions, and the pallet–forklift combo trounced the competition. The Quartermaster General ordered a million pallets, and the domestic pallet industry was effectively born.5

There is a war brewing in Pallettowne. Read the whole thing.

2014 in review

The WordPress.com stats helper monkeys prepared a 2014 annual report for this blog.

Here's an excerpt:

A New York City subway train holds 1,200 people. This blog was viewed about 5,200 times in 2014. If it were a NYC subway train, it would take about 4 trips to carry that many people.

Click here to see the complete report.

Critique of Citizen Sleuths Probability Calculation of DB Cooper’s Tie

The DB Cooper Case is notable for its lack of physical evidence. On the airplane, Cooper left behind some cigarette butts, two leftover parachutes, a glass he used and a black clip-on tie. The cigarettes were misplaced and are considered lost, there may or may not be DNA in evidence from them. Cooper’s fingerprints were likely collected from the airplane, as about 60 sets of fingerprints were recorded. The big piece of evidence was the tie. Recent testing done by Tom Kaye has uncovered evidence on the tie [found on Cooper’s seat] that gives the clearest profile yet of who Dan Cooper was before the heist. Since it can’t be known for sure if the tie was actually Coopers, Kay et al performed a probability analysis.

Here are the components of the CS team analysis: 1) Twenty passengers potentially leaving a tie on Cooper’s flight including Cooper. 2) Forgetting the tie on the plane = 15% (best estimate). 3) Leaving the tie on Coopers seat = 5% (best estimate). 4) Smoker = 44% (percentage of males who smoked in 1970). 5) Passengers wearing a black tie = 35% (best estimate). From these numbers, it is concluded there is a “98% probability” the tie belongs to Cooper.

There are a few areas where Kaye and his team might have gone wrong. Most glaringly is the fact, with the back door of the aircraft open and a man jumping off the airstairs while in flight, the cabin in the aircraft would have experienced significant pressure changes, making the odds a tie landed on Cooper’s seat after being blown from somewhere else, much higher. To give a more conservative estimate, variable #3 should be adjusted upwards, perhaps to as high as 25%. This adjustment gives us an approximate 90% probability the tie belongs to Cooper. Still high enough to affirm Kaye’s later analysis of the particles on the tie, but it does not cross the “two sigma threshold” Carr concludes. It’s a minor point, but an important one.


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