Stats Chat

Q: Did you see “Just one extra banana or avocado a day could prevent heart attacks and stroke”

A: Hmm.

Q: It’s the potassium

A: Uhuh

Q: New Research Suggests

A: The effects of higher-potassium foods on blood pressure aren’t ‘new research’.  Look at what the American Heart Association says, or Harvard Health.

Q: Those sites don’t mention avocados, though. Is that what was new about the research?

A: No, that’s probably to meet the day’s quota for avocado stories.

Q: But at least the health message is real? They quote the researcher “The findings demonstrate the benefit of adequate potassium supplementation on prevention of vascular [hardening]”. With proper brackety things like we tell students to use.

A: We might prefer students to quote the rest of the clause , as the story does later: “demonstrate the benefit of adequate potassium supplementation on prevention of vascular calcification in atherosclerosis-prone mice” (emphasis added)

Q: So it probably wasn’t bananas, either.

A: No, high-cholesterol, high fat mouse food with high or low potassium.

Q: But the high-potassium mice lived longer? They had fewer heart attacks and strokes?

A: This is a lab experiment. It’s never going to end well for the mice. But they had stretchier arteries while they were alive.

Q: So what was the point, if we already knew higher-potassium diets with lots of fruit and veg are good for blood pressure?

A: The point was to find out how it works — which genes and proteins and so on.

From the world’s third-largest news agency:

1. The Nationalist Party?
2. National got 56 seats, not 58 — the graph seems to have the National results from the provisional count but the Labour and Green results from the final count
3. NZ First doesn’t use yellow
4. ACT, on the other hand, does.
5. But ACT is relatively unlikely to enter a left-wing coalition with Labour and the Greens

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 62 matches played, 43 of which were correctly predicted, a success rate of 69.4%.
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 14

The basic method is described on my Department home page.

After trying to deal with the Cheetahs playing their first team in the Pro14 and a second or third team in the Currie Cup, I have come up with the appropriate solution, which is to have two separate Cheetahs teams. Cheetahs is the team when there is no Pro14 game, so the first choice players should be playing. Cheetahs2 is the team when there is a Pro14 game that week, so the reserve players will be playing in the Currie Cup.

I arbitrarily started the Cheetahs2 at a rating of -30, which is a bit of a rough guess based on results so far, and reran all my predictions so far to produce this weeks predictions. Note that the Cheetahs2 rating has not changed very much over the games so far, nor has the rating for the Cheetahs.

I would welcome comments on the assumptions underlying this approach.

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 39 matches played, 26 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Round 14

Here are the predictions for Round 14. 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.

• Google has a camera that learns to take automatic videos of your kids and pets.  And they’ve gone to some lengths to make it less creepy than that sounds.

• It’s not just the inbuilt biases of the input data you have to worry about in statistical models/machine learning. People are also messing with the input deliberately.

• NY Times piece on personal genetic testing. (Disclaimer: I’m doing some consulting for a personal genomics company)

• Also from the Times, Jordan Ellenberg (mathematician) on “How Computers Turned Gerrymandering Into a Science“ (Now with a link!!)

• Where Americans get their science news and how much they trust various sources, from Pew Research.

• “The Subjects Planned for the 2020 Census and American Community Survey report released today inadvertently listed sexual orientation and gender identity as a proposed topic in the appendix,” the U.S. Census Bureau said in a statement to NBC News. “This topic is not being proposed to Congress for the 2020 Census or American Community Survey”

• ” It’s no longer good enough to shrug off (“briefly,” “for a small number of queries”) the problems in the system simply because it has computers in the decision loop.”

• Road deaths are up since 2013.  Contrary to what the NZTA spokesperson says, it can’t be explained by increases in cars on the road: there has been a change in the trend for deaths per unit distance travelled.

• Voting is now open for NZ Bird of the Year.  StatsChat doesn’t usually endorse bogus polls, but this one admits it’s just a publicity stunt.

Each week, we would like to invite readers of Stats Chat to submit nominations for our Stat of the Week competition and be in with the chance to win an iTunes voucher.

Here’s how it works:

• Anyone may add a comment on this post to nominate their Stat of the Week candidate before midday Friday October 13 2017.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of October 7 – 13 2017 inclusive.
• Quote the statistic, when and where it was published and tell us why it should be our Stat of the Week.

Next Monday at midday we’ll announce the winner of this week’s Stat of the Week competition, and start a new one.

(more…)

The last 127 people to win a Nobel Prize for Physics have been men. Various people have calculated probabilities for this under a model where the true probability each time is 50:50.  Those probabilities are very small: they start with 37 zeros. Now, as people who analyse coincidences will tell you, there’s potential for cherry-picking. Gender of Nobel Laureates in Physics isn’t the only possible comparison.  On the other hand, if the comparison were picked from a thousand million billion trillion competing comparisons, the probability would still be tiny. The hypothesis that the committee chooses people at random for the Nobel Prize in Physics is not statistically defensible.  In fact, even the hypothesis that the committee chooses people with physics PhDs at random isn’t statistically defensible.

The reason there’s still controversy is that ‘choosing people at random’ isn’t anyone’s claim about how the Nobel Prize in Physics works.  Roughly speaking, there are three explanations for it just being given to women:

1. Physics is too hard for women, who should just stick to biostatistics
2. Women don’t get many opportunities to lead really ground-breaking physics research, because science is sexist
3. The Nobel Committee for Physics (or the people eligible to nominate) are less likely to choose women who have contributed just as much

The p-value with a ridiculous number of zeros doesn’t provide any basis for assessing how important the three explanations are.  You need more data — and a different type of data.

So, for example, it’s relevant that Lise Meitner was nominated 29 times for the prize (and 19 times for the Chemistry prize) and didn’t win, but that Otto Hahn did win for their joint work. It’s relevant that Chieng-Shieng Wu was nominated 7 times and that a prize was awarded for the discovery she worked on. It’s relevant that Vera Rubin received lots of other prizes and awards and was routinely mentioned as a possible Nobelist — we don’t yet know how often she was nominated because there’s a 50-year secrecy rule.

Personally (though I’m not a physicist) I think that explanation 1 can be largely discounted and explanation 2 has to stretch a lot to cover the situation, so explanation 3 is looking plausible. But the numbers with 37 zeroes aren’t a relevant summary of the data.

• The Crowd Counting Consortium: A project to count crowds at demonstrations in the US

• Data leakage: Bluetooth sex toys do not have a good sense of what’s a private activity (probably NSFW)

• “It would reason as you might run, but without tiring so long as it had electric power. Awesome. This is exactly not what deep learning systems deliver.” Alex Harrowell on perceptrons and their machine-learning grandchildren.

• “Science in Society” award winners from the (US) National Association of Science Writers

• The Nobel Prize for Physics went to gravitational wave astronomy. That’s a more statistical area than usual — extracting minute gravitational-wave signals from the background noise is a statistical challenge as well as an engineering nightmare. Renate Meyer, from the UoA Statistics department, and her co-workers, did some of the early work on this problem, and Matt Edwards (who we’re hoping to get back after a postdoc overseas) is a member of the LIGO Consortium.

• “Personal genetic testing is here: do we need it?” from the New York Times.

From Stuff, the front-page link:

As Betteridge’s Law of Headlines implies, the answer is “No.” Even the vendor doesn’t make a claim like that.

The story says (with the advertising redacted)

The key ingredient in the capsules is 100mg of … a blend of grapefruit and rosemary extracts. An independent lab trial of [the stuff] in Italy in 2015 found the onset of sunburn was delayed by 30 percent after two months of daily use.

It appears to be still-unpublished study. According to an advertising white paper,  it’s actually better than a lot of nutraceutical research: it was blinded and had 35 people in each group.  If we assume there aren’t any hidden problems, the study says that people who take this stuff daily for a couple of months end up needing about 30% more UV light to get a mild sunburn.

That is, the optimistic view is we’re looking at the equivalent of SPF 1.3 sunscreen.

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 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 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.