Stats Chat

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.

Team Ratings for Round 8 Delayed Match

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 68 matches played, 52 of which were correctly predicted, a success rate of 76.5%.
Here are the predictions for last week’s games.

Predictions for Round 8 Delayed Match

Here are the predictions for Round 8 Delayed Match. 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.

• Self-selected responses: this Twitter thread by Patrick Tomlinson is about the large number of negative reviews his book has on Goodreads. The book is still being edited. It won’t be available for months.
• From the Washington Post: “Our privacy experiment found that automakers collect data through hundreds of sensors and an always-on Internet connection. Driving surveillance is becoming hard to avoid”.
• Via the Herald: surprising no-one, a study by the US National Institute of Standards and Technology has found that US facial-recognition algorithms are better at recognising white people.  (Algorithms developed in east Asia seem to be ok at east Asian faces.)
• Last year I mentioned investigations at newsroom.co.nz by Eloise Gibson and others of Sir Ray Avery. Sir Ray filed a Media Council complaint about a story that alleged he had threatened a researcher with legal action. The Media Council has found in favour of newsroom
• From Radio NZ “Plans to collect data by putting sensors in thousands of state houses could result in the information being used to cut benefit payments or even evict tenants, a charity familiar with the project says.” The goal of the sensors is to find out what the actual heating/ventilation/damp problems are with state houses, information that would generalise to many other NZ houses. That’s a valuable goal. And Kāinga Ora say they don’t want to do anything else with the data, such as identify overcrowding or check who regularly has visitors staying the night,  or other potentially creepy possibilities.  But there doesn’t seem to be any clear mechanism to stop Kāinga Ora changing their minds.   Given the potential public benefits from suitable analyses of the data, it would be worth setting up a mechanism that people could see was trustworthy, rather than ending up with crap data when too many people opt out.
• Interpreting survey responses: The New York Times had an interactive clicky thing asking people to identify celebrities from their photographs.  Pete Buttigieg’s name was spelt in 268 different ways (click to embiggen). Presumably these weren’t all serious, but that doesn’t actually make life any easier for the survey analyst.
  

Auckland went impressively dark just before 2pm this afternoon: from Christina Hood on Twitter:

The reason is smoke from the Australian bushfires.

Fortunately for Auckland, the smoke (at the moment) is mostly at high altitude; you can tell because the lower picture is about as clear as the upper picture, just darker and more orange. Fine air pollution particles scatter light very effectively — in places with less humid summers than Auckland, light scattering is a good way to measure how much there is.

We can also look at the hourly measurements of PM2.5; fine-particle air pollution, or, basically, smoke.  Here are data from Penrose, in south central Auckland.

and Patumahoe, in far south Auckland

I chose these two because they were available and because there won’t be that much NZ-origin air pollution at those sites (on a Sunday afternoon).  At both locations there’s been an increase in fine particle air pollution, but not to any level of health concern.  It might be worth looking later in the evening, if you’re worried.  Given the placebo effect, if you don’t have specific health concerns you might be better off not checking.

(The Environment Auckland permalinks don’t work, so you need to go here and then to the AQ locations link, and then drill down.  You want “PM2.5 Hourly Aggregate unverified”)

This smoke used to be trees, 2000km away. We’ve seen particles from further than that — the Puyehue-Cordon Caulle volcano in Chile disrupted flights in 2011 — but the density of this smoke is much, much higher. WeatherWatch doesn’t know of a precedent.

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 61 matches played, 48 of which were correctly predicted, a success rate of 78.7%.
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 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 42 matches played, 31 of which were correctly predicted, a success rate of 73.8%.
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.

My apologies for the late publication of these predictions. I was too distracted by Christmas.

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 55 matches played, 42 of which were correctly predicted, a success rate of 76.4%.
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 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 36 matches played, 27 of which were correctly predicted, a success rate of 75%.
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.

Betelgeuse, the bright red star at the base¹ of Orion, has suddenly dimmed, enough that people who aren’t astronomers may be able to tell by looking at it.

Here’s a simple graph. Yes, the y-axis goes down rather than up.  Astronomers are weird that way.

Here’s a more detailed version of the same thing, from the AAVSO website, which includes all the available observations. You can see that the latest dimming did pretty much coincide with the UK election²

As StatsChat readers will know, it’s unwise to draw strong conclusions from a short time series if a longer one is available.  I asked the AAVSO webserver for all its Betelgeuse data. I trimmed off some clearly outlying values (if it weren’t Christmas I would have asked an astronomer first).

Here’s the graph for this year

The gap in autumn/winter is because Betelgeuse is out during the day at that time of year, and so isn’t visible except in Antarctica.

Here’s all the values between 2 and -1 magnitude, back as far as AAVSO collects. There’s been a decrease since

So, while the current dimming is extreme,  it also looks like this is a thing Betelgeuse does.  That’s what astronomy twitter is saying.

There’s been media coverage of the dimming, including speculation that the star is about to go supernova.  Mostly, the reports have been good: saying that it could go any time, but pointing out that ‘any time’ on astronomical time scales means any time between 700 years ago and 100,000 or so years in the future.

1. StatsChat is in the southern hemisphere

2. Well, except for the time lag of about 700 years in the light getting here. They must have very good long-range polling on Betelgeuse. They probably use MRP.

The Accident Compensation Corporation, a wonderful NZ institution, always takes advantage of the season to try to get coverage of Christmas accident risks. There are two popular angles, and this year our newspaper sites have one each.

The NZ Herald writes about the total cost of Christmas claims.  These, according to the story, are steadily increasing: $448k in 2014, $497k last year. The increase, of nearly 11%, needs to be compared to the population increase of about 8.4% (June 2014 to June 2018) and to inflation of about 5%.  Christmas accident claims have increased very slightly per capita in nominal dollars, and decreased very slightly per capita in constant dollars.  And, as the story admits, Christmas Day is not a particularly high-risk day — it’s compared there to New Year’s Day, but it actually has lower ACC costs than a typical day.

On Stuff, the story is about holiday-specific accidents. Here we’re on stronger ground.   The Christmas tree, pavlova, and turkey injuries are reliably attributable to Christmas; we’re talking causation, not just correlation.  If I were feeling pickier than is appropriate for the season, I might complain about “Turkey was a slightly safer option”  comparing turkey and ham-related injuries: we don’t know that turkey was safer, since we’d need the number of people at risk from turkey and ham to draw that conclusion.

The song referenced in the title makes clear the difference between injuries occurring at Christmas and those caused by the season — “she had hoof-prints on her forehead / And incriminating Claus marks on her back”.  Even though there are fewer injuries on Christmas Day, we can still tell that some of them are Christmas injuries. It makes sense for ACC to try to reduce these, especially given the reduced competition for news coverage at this time of year.