Stats Chat

The Herald (on Twitter, today)

An international study has revealed why Auckland has been ranked low for liveability compared to other cities in New Zealand and the rest of the world.

Stuff (March last year)

The City of Sails continues to be ranked the world’s third most liveable city for quality of life.

Phil Goff, as Mayor of Auckland, obviously prefers the pro-Auckland survey and the Herald said he ‘rubbished’ the other survey, saying it “defies all the evidence which shows Auckland is a growing, highly popular city for all people.”

There’s no need for one survey to be wrong and the other one right, though. It depends on what you’re looking for.  Mercer’s rankings (where Auckland does well) are aimed at companies moving employees to overseas postings. One of their intended uses is to work out how much extra executives need to be paid in compensation for living in, say, Houston or Birmingham rather than Auckland or Vancouver.   Cost of living doesn’t factor into this; it’s quality of life if you’re rich enough.

Some of the quality of life features (good climate, safe streets, lack of air pollution) can be enjoyed by most people, but some really are more relevant if you’ve got money.

The Movinga ranking that the Herald quotes is about suitability for families.  Two important components are housing costs, and total cost of living, in terms of local incomes.  Auckland does fairly badly there, and also on a public transport/road congestion component.  The ranking of 94 out of 150 overstates the issue a bit: here’s the distribution of scores, with Auckland in yellow. Auckland is part of the main clump, where the rankings will be sensitive to exactly how each component is weighted.

There are important reasons to want to live in a particular city that neither ranking considers.  An obvious one is employment or business opportunities.  If your speciality is teaching statistics or installing HVAC in tall buildings or running a Shanxi restaurant, you’ll probably do better in Auckland than in New Plymouth.  Movinga also rates cities on suitability for entrepreneurs, jobseekers, and as places to find love (Auckland is 34th out of 100 on that last one).

As Betteridge’s Law of Headlines says, the correct response to any headline ending in a question mark is “No”.

From the Herald: “Kogan Mobile – a relative newcomer to NZ – is offering $1 million if you can correctly pick the result of every game in the first six rounds of the new Super Rugby seasons.”

This is a good deal for Kogan Mobile. They get coverage in the Herald and on NewstalkZB (albeit at 5:20am), and they get a lot of email addresses, many of which will be genuine.  There will be people who hadn’t heard of the company last week who now have heard of them.

I shouldn’t think the publicity is worth a million dollars, but they’re very unlikely to have to pay out.  As I told Chris Keall and Kate Hawkesby, if you typically average 2 out of 3 correct predictions (roughly what StatsChat’s David Scott gets), you’ve got one chance in ten million of getting forty correct predictions — to be precise, (2/3)⁴⁰

It’s actually a bit worse than that. David gets two out of three correct, but there are easy picks and hard picks, and he does better on the easy ones than the hard ones.   Variation in difficult makes it harder to get all the picks right  — imagine someone who was 100% wrong whenever the Hurricanes played the Chiefs; they could still average two out of three, but they couldn’t get 40 out of 40.

The variation in difficulty doesn’t make that much difference. Suppose you had a 50:50 chance for 29 of the games and the other 11 were so easy you had a 100% chance. That averages close to 2/3, and the variation is more extreme than really plausible, but the chance of getting all forty correct is (0.5)²⁹×(1)¹¹, or one in 500 million, only lower by a factor of 50.

If Kogan Mobile get a million entries, which seems quite a lot for New Zealand, they’d still have probably less than one chance in ten of paying out.   They might have decided to wear that chance, or they might have bought insurance — in 2003, when Pepsi offered a billion dollar lottery-style prize, they insured the risk of paying out, for less than $10 million.

So should you play? Sure, if you feel like it.  You just shouldn’t expect much of a chance of winning.

Team Ratings for Round 1

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.

Predictions for Round 1

Here are the predictions for Round 1. 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.

There’s a revolutionary hypothesis about the cost of US healthcare: that it’s driven by the extreme, chronic costs of a few people.  These people have problems that go far beyond medicine, but they could be helped by high-level, individualised social services and support, that would still be cheaper than their medical costs.  Atul Gawande wrote a famous article in the New Yorker on the topic.

In Camden, New Jersey, a program of this sort has been in place for several years.  A new research paper says

The program has been heralded as a promising, data-driven, relationship-based, intensive care management program for superutilizers, and federal funding has expanded versions of the model for use in cities other than Camden, New Jersey.To date, however, the only evidence of its effect is an analysis of the health care spending of 36 patients before and after the intervention and an evaluation of four expansion sites in which propensity-score matching was used to compare the outcomes for 149 program patients with outcomes for controls

What we need here is a randomised trial.  Impressively, given that the program has been famous, and has already been expanded into other cities, the Camden Coalition did a randomised trial, comparing the promising, data-driven, relationship-based, intensive care management program to treatment as usual.  As the New York Times reports

• Reuters graphics showing the size of the Australian bushfires
• From Jen Hay (linguist) on Twitter Karl du Fresne recently wrote: “The year just passed was notable for the supplanting of the letter T by D in spoken English, so that we got authoridy in place of authority, credibilidy instead of credibility, securidy for security, and so on”. Professor Hay goes on to point out that this is a long-standing trend in NZ English, and show that du Fresne himself was doing it as long ago as 2013!
• On cancer hype (via Derek Lowe) By email or through their press representatives, STAT asked 17 of the leaders who were quoted in that press release to reflect on what the moonshot has and hasn’t accomplished in the past four years. None of them agreed to comment.
• Also from Derek Lowe, about cancer trends.  Some cancers are occurring at the same rate they used to, but people aren’t dying from them (good). Some are occurring less often than they used to (good). Some are occurring much more often than they used to, but no more people are dying from them.  That sounds as though it might be good, but (at least in part) it will be overdiagnosis — the cancers aren’t really getting that much more common, we’re just diagnosing harmless cases.
• 538 are giving forecasts for the US primary elections — including uncertainty intervals, which are really wide still. In 80% of simulations, [Biden] wins between 5% and 45% of the vote. He has a 3 in 10 (30%) chance of winning the most votes, essentially tied with the second most likely winner, Sanders, who has a 3 in 10 (28%) chance.

Morning Consult and Politico run a survey where they asked registered US voters to point Iran out on a map.  About a quarter could. Here are the complete results

As you will notice, there are dots everywhere. Morning Consult didn’t go in for any grandiose interpretations; they just presented the proportion of respondents getting the answer correct. Other people were less restrained. There was much wailing and gnashing of teeth over this map, on Twitter, but also at other media outlets.  For example, Rashaan Ayesh wrote at Axios

While the Middle East saw definite clustering, some respondents believed — among dozens of wild responses — that Iran was located in:

• The U.S.
• Canada
• Spain
• Russia
• Brazil
• Australia
• The middle of the Atlantic Ocean

The claim that some respondents believed Iran to be in the US or the middle of the Atlantic ocean is worrying to me.   I can’t see how a sensible journalist could possibly state as a fact that someone had a belief like that based just on the incredibly flimsy evidence that there’s a dot there on the map.  I’d want to at least have someone explicit claim that they thought Iran was in the middle of the ocean, and ideally have follow-up questions asked about where they think Iranians keep their mosques and carpets and where they grow their rice and barberries and pomegranates and walnuts and so on.

It’s a well-known phenomenon that people don’t always give the answers you want on surveys. Scott Alexander has written about the ‘Lizard-man constant’, and that’s even before you give people a clicky interactive map to play with.   It’s barely conceivable — no, actually it isn’t, but let’s pretend it is — that some people think that large continent on the upper left of the map is the Middle East, or recognise it as North America but believe Iran is in the US.

It seems much more likely to me, though, that

• they don’t know where Iran is and would rather give an obviously wrong answer than look as if they’re trying
• they clicked wrong on the map, because interactive maps are actually kind of a pain to use, especially on a phone.
• they think having heard of Iraan, Texas (pronounced Ira-an), or Persia, Iowa, will make them look clever.
• they want to mess up the survey because they hate polling or for political reasons or because they’re having a bad day

The next question, of course, is how much it matters that the majority of US voters couldn’t find Iran on a map.  Iran is relatively easy, as countries go — I knew that it had a coastline on the Persian Gulf and that it wasn’t on the Arabian Peninsula, and Iran is big enough that this is sufficient.  But suppose I thought it was where Iraq is, or Syria, as many people did. Should have an impact on my political views (assuming I’m in the US)?  It’s not clear that it should.  The potential ability of Iran to close the Straits of Hormuz (and the Doha and Dubai airports) does depend on its location, but the question of whether the US was justified in killing Qasem Soleimani or threatening to bomb Iranian cultural sites doesn’t seem affected.

There’s a story by Brittany Keogh at Stuff on misconduct cases at NZ universities (via Nicola Gaston).  The headline example was someone bringing a gun (unloaded, as a film prop). There were 1625 cases of cheating.

As with crime data, there are data collection biases here: whether or not things are reported to the university, and whether the university takes any action, and whether that action ends up as a misconduct record, and how that record is classified.   Notably,

Victoria University of Wellington was the only university that noted disciplinary cases for sexually harmful behaviour, with three incidents reported in 2018. 

The university defined sexually harmful behaviour as “any form of unwelcome sexual advance, request for sexual favours, and any other unwanted behaviour that is sexual in nature”, including sexual harassment or assault.

There’s no way there were only three cases at universities. Or only three cases reported to universities.

The under-reporting is not quite as bad as that: the University of Canterbury reported ‘several’ harassment cases that resulted from a Law Society review into sexual misconduct, so we’ve got a classification problem as well.  Some of the harassment cases at other universities might also be included.  And there’s no data from Otago (which hasn’t responded) or Massey (which refused).

It’s definitely possible to go too far the other way — in the US, Federal law requires reporting and investigation for all incidents, even in the absence of a complaint, which means that a victim who doesn’t want to be put through an investigation is quite limited in who they can talk to.

With these numbers, though, the big story shouldn’t be that someone once brought an unloaded gun to campus with no violent intent; it should be that the universities are managing not to notice sexual harassment and assault.

There are lots of maps going around of the Australian fires. Some of them are very good, others indicate ways you can accidentally or deliberately mislead people.

This one was created as a 3-D visualisation by Anthony Hearsey, based on infra-red hotspot data accumulated over the fire period. It has been circulated as a ‘NASA photo’, which it isn’t.

If you think of it as a map or photo, the image exaggerates the scale of the fires by accumulating burning areas over time, and by the ‘glow’ effect in the 3-d rendering.  As Nick Evershed, a Guardian data journalist, points out, it is also exaggerated because it ’rounds up’ each spot of fire into a whole map grid square.  Nick produced this version with the accumulated fires over time but without the rounding and glow.

A much more effective way to mislead with maps, though, is just to make stuff up and not worry about the facts.  Yesterday, ABC News (the US one, not the Australian one) gave this map (insightful annotation from Buzzfeed)

They now have this one. It still make the fire areas look larger than they are, but in standard and hard-to-avoid ways.

A note at the end of the story now says

Editor’s note: The previous graphic in this story has been updated to reflect the hot spots around Australia.

Maybe it’s a matter of taste, but I don’t think that goes nearly far enough towards admitting what they did.

Q: Did you see that going to the opera makes you live longer?

A: No, it just makes it feel longer

Q: ◔_◔

Q: This story, from the New York Times.

Now, there is evidence that simply being exposed to the arts may help people live longer.

Researchers in London who followed thousands of people 50 and older over a 14-year period discovered that those who went to a museum or attended a concert just once or twice a year were 14 percent less likely to die during that period than those who didn’t.

A: Actually, if you look at the research paper, they were just over half as likely to die during the study period: 47.5% vs 26.6%. And those who went at least monthly were only 60% less likely to die: 18.6% died.

Q: You don’t usually see the media understating research findings, do you?

A: No. And they’re not.  The 14% lower (and 31% lower for monthly or more frequent) are after attempting to adjust away the effects of other factors related to both longevity and arts/museums/etc

Q: You mean like the opera is expensive and so rich people are more likely to go?

A: Yes, although some museums are free, and so are some Shakespeare, etc,

Q: And if you can’t see or hear very well you’re less likely to go to opera or art galleries. Or if you can’t easily walk short distances or climb stairs?

A: Yes, that sort of thing.

Q: So the researchers didn’t just ignore all of that, like some people on Twitter were saying?

A: No. The BMJ has some standards.

Q: And so the 14% reduction left over after that is probably real?

A: No, it’s still probably exaggerated.  Adjusting for this sort of thing is hard.  For example, for wealth they used which fifth of the population you were in. The top fifth had half the death rate of the bottom fifth, and were five times as likely to Art more often than monthly.  For education, the top category was “has a degree”, and they were half as likely to die in the study period and 4.5 times more likely to Art frequently than people with no qualifications.

Q: “Has a degree” is a pretty wide category if you’re lumping them all together.

A: Exactly.  If you could divide these really strong predictors up more finely (and measure them better), you’d expect to be able to remove more bias.  You’d also worry about things they didn’t measure — maybe parts of the UK with more museums also have better medical care, for example.

Q: But it could be true?

A: Sure. I don’t think 14% mortality rate reduction from going a few times a year is remotely plausible, but some benefit seems quite reasonable.

Q: It might make you less lonely or less depressed, for example

A: Those are two of the variables they tried to adjust for, so if their adjustment was successful that’s not how it works.

Q: Isn’t that unfair? I mean, if it really works by making you less lonely, that still counts!

A: Yes, that’s one of the problems with statistical adjustment — it can be hard to decide whether something’s a confounding factor or part of the effect you’re looking for.

Q: But if people wanted to take their kids to the museum over the holidays, at least the evidence is positive?

A: Well, the average age of the people in this study was 65 at the start of the study, so perhaps grandkids.  Anyway, I think the StatsChat chocolate rule applies: if you’re going to a concert or visiting a museum primarily for the health effects, you’re doing it wrong.

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 48 matches played, 36 of which were correctly predicted, a success rate of 75%.
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.