Stats Chat

• From the journal BMJ “Data about the timing of when laboratory tests were ordered were more accurate than the test results in predicting survival in 118 of 174 tests (68%).” In particular, for one of the tests they looked at, having the blood test ordered at 5am (regardless of the result) was more of a bad sign than having it ordered at 5pm and giving an unfavourable result.  This isn’t all that surprising: if you get lab tests ordered at 5am there’s a problem, and a favourable result for the test just means the problem isn’t the one that the test was looking for. But it is potentially a problem for interpreting conclusions from large-scale data mining or, to be fair, from uninformed statistical analysis.
• NBC News in Chicago did a story on direct-to-consumer genetic testing. As several journalists have done, they sent a DNA sample to multiple testing companies and compared the results.  They also did the same thing with a sample from a Labrador.  Most of the companies said the dog’s DNA didn’t genotype successfully. Most, but not all.
• Tim Harford recommends books on understanding data-driven prediction algorithms
• A talk by Jonathan Korum of the New York Times on graphics for science stories
• From Karl Broman and Kara Woo: “Data Organization in Spreadsheets” If you, or someone you know, uses spreadsheets …
• How to display uncertainty in election predictions. From The Crosstab.
• Someone in the US was hit by lightning, bitten by a shark, bitten by a venomous snake, and attacked by a bear in one year. National Geographic says

Since each event is independent the odds of each are multiplied together, he said, making the odds of this happening 893.35 quadrillion to one.

         Of course, they really aren’t independent — and the next sentence pretty much points this out

McWilliams just chalks all this up to being in the wrong place at the wrong time. He encourages everyone to experience the outdoors. “I still go hiking, I still catch rattlesnakes, and I will still swim in the ocean,

Here’s a blog post from CSIRO “Bloody data: biostatistics and the first blood test for Alzheimer’s”

Here are some of the media headlines:

New blood test detects Alzheimer’s disease up to 20 years before symptoms begin

New blood test could detect risk of Alzheimer’s disease 30 years early

‘Holy grail’ blood test for early Alzheimer’s indicators could help patients begin treatment before they show symptoms

World-first blood test to diagnose dementia

Science has created a simple blood test for Alzheimer’s

Here’s the research paper and  two press releases about it: from the Florey Institute and from Melbourne Uni 

As StatsChat readers will know, this isn’t the world-first early test for Alzheimer’s to end up in the media.  And as you’ll expect, the test hasn’t actually been able to detect Alzheimer’s disease 20 or 30 years before symptoms begin. That would require either waiting 20 or 30 years to see who developed symptoms, or having a test that could be run with blood samples from 20 or 30 years ago.

What the test actually does is predict quite accurately how much amyloid-beta protein people have in their brain using just a blood sample. That’s useful, because the current ways of measuring amyloid in the brain are expensive and involve radiation and/or sampling fluid from the spine, and these aren’t things anyone wants to do at the level of population screening.

We don’t currently know if measuring amyloid in the brain gives good 20-year predictions of Alzheimer’s — there’s increasing suspicion that the relationship between Alzheimer’s and amyloid is more complicated than was thought.   But it’s the best candidate we’ve got for an early test, and a low-cost, low-risk, low-pain version of it would be very useful in selecting people for clinical trials targeting amyloid levels — as I’ve said about a few of the other “first blood test for Alzheimer’s” candidates.

The research paper did look at using the test to distinguish people with definite, known Alzheimer’s from a healthy comparison group.  They found the test picked up almost all of the Alzheimer’s cases, but gave false positives in nearly 20% of the healthy controls.  Maybe that’s just saying that 20% of the controls will end up with the disease in 20-30 years, but there’s no way to know that in the short term.

This is good research, giving a genuine improvement on an important component of one step in testing potential future drugs to prevent Alzheimer’s. And the actual text of some of the stories is quite reasonable.  The headlines, however, are actively misleading, because of the need to frame science stories as  breakthroughs.

This isn’t the Holy Grail. Indiana Jones isn’t just ten minutes and three plot twists away from the final credits. That just isn’t how science typically works.

Team Ratings for Round 12

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 67 matches played, 48 of which were correctly predicted, a success rate of 71.6%.
Here are the predictions for last week’s games.

Predictions for Round 12

Here are the predictions for Round 12. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 9

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 64 matches played, 33 of which were correctly predicted, a success rate of 51.6%.
Here are the predictions for last week’s games.

Predictions for Round 9

Here are the predictions for Round 9. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 22

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 126 matches played, 87 of which were correctly predicted, a success rate of 69%.
Here are the predictions for last week’s games.

Predictions for Round 22

Here are the predictions for Round 22. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 11

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 61 matches played, 44 of which were correctly predicted, a success rate of 72.1%.
Here are the predictions for last week’s games.

Predictions for Round 11

Here are the predictions for Round 11. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 8

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 56 matches played, 29 of which were correctly predicted, a success rate of 51.8%.
Here are the predictions for last week’s games.

Predictions for Round 8

Here are the predictions for Round 8. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

From Stuff: One in six Kiwi drivers use their phone at traffic lights, poll finds

This is a bogus poll from Neighbourly, the local bulletin board/discussion site owned by Stuff‘s publisher.  It’s based on “more than 3900” self-selected members of the site, without any attempt to make the figures representative. And that’s before you get to the issue of how honest people are being about their law breaking.

There’s almost no limit to how wrong bogus polls can be. Thanks to anchoring bias, there’s a good chance you’re better informed if you don’t see the results than if you do.

For a while, the NZ media had stopped writing stories and headlines based on bogus polls, but it’s been starting up again.

Team Ratings for Round 10

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 54 matches played, 38 of which were correctly predicted, a success rate of 70.4%.
Here are the predictions for last week’s games.

Predictions for Round 10

Here are the predictions for Round 10. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 7

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 48 matches played, 25 of which were correctly predicted, a success rate of 52.1%.
Here are the predictions for last week’s games.

Predictions for Round 7

Here are the predictions for Round 7. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.