Posts filed under General (3152)

Team Ratings for Round 13

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 92 matches played, 52 of which were correctly predicted, a success rate of 56.5%.
Here are the predictions for last week’s games.

Predictions for Round 13

Here are the predictions for Round 13. 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.

As you might have read in an English class (at least if you’re old) “The past is a foreign country: they do things differently there.” In particular, they buy things differently.

We often want to compare prices between the present and the past. To compare prices between here and actual foreign countries, we use the exchange rate and find, for example, that the US cost (from Amazon) of Sennheiser CX 3.0 earphones, US$29.99 is equivalent to about NZ$40, or about NZ$46 with tax.  We can then straightforwardly say that Harvey Norman is charging 60% more  than Amazon for the same item, and force them to make unconvincing excuses.  Comparing foreign prices can get complicated if you’re interested in affordability relative to income, or if you’re looking at a country with very restrictive border controls but the existence of two-way trade with many foreign countries means there is a single, well-defined exchange rate.

The equivalent conversion for past prices is an inflation adjustment. If you’re comparing past and current prices without an inflation adjustment you’re not even trying to get the numbers right (with a few very limited exceptions such as bracket creep).  There should be an automatic presumption of dodginess for any `nominal’, unadjusted comparison of amounts of money at different times — especially as this is something that’s really easy to get (approximately) right.  So, go and fix it now.

I said “approximately right”, and those of you still with me will note that we don’t have extensive two-way trade with the past. Inflation isn’t as simple as an exchange rate.You can’t buy Sennheiser CX 3.0 earphones with 1997 dollars, and even if you could, Amazon would have difficulty shipping them to 1997.  Inflation adjustments are more like the Economist‘s Big Mac purchasing-power index.  The magazine decrees that Big Macs have the same true value everywhere in the world, and so can estimate the relative value of different currencies.  That’s not ideal when comparing countries, and it’s even harder when comparing with the past.

Economists and official statistics agencies make up ‘baskets’ of items and decree these to have the same value over time, carefully making sure that the items are defined narrowly enough for ‘the same value’ to be reasonable, and broadly enough that you can still find ‘the same item’ a year later.  They also make complicated adjustments for changes in quality of the ‘same item’ (math is hard even if you go shopping).  That’s really the only way you can do it, and it works ok for many purposes, but there isn’t just one inflation rate the way there is one exchange rate.

Macroeconomists use this thing called ‘core inflation’, which leaves out items that vary a lot in price and which they say predicts macroeconomic things better.  There are indexes based on baskets of items bought by NZ producers, or sold by NZ producers.  There are indexes based on baskets of items relevant to different sorts of households: Graeme Edgeler has a nice post pointing out that there is an inflation index targeted to beneficiaries, and that it would make sense to use this to index benefits (he also drafted a bill).

The other tricky part of the basket approach to comparing past and current prices is the huge differences between items.  The prices of computers, washing machines, t-shirts, and old-enough medications are increasing more slowly than the average inflation rate; they are getting systematically less expensive ‘in real terms’. By simple arithmetic, that means the prices of other things must be rising faster than the average inflation rate; they must be getting more expensive ‘in real terms’.

It sounds odd to say that primary schools or health care are getting more expensive to run `in real terms’ because computers and t-shirts are cheaper — but it’s partly true. Some sort of currency conversion is always necessary when comparing different currencies — the 2001 dollar and the 2017 dollar — but it’s not always sufficient.

(Alastair didn’t contribute directly to StatsChat, but he was a major contributor to this being a department that would take it seriously.)

In memoriam: Alastair Scott, Emeritus Professor of Statistics (1939-2017).

Alastair Scott, one of the finest statisticians New Zealand has produced, died in Auckland, New Zealand on Thursday, May 25. He served the University of Auckland with distinction from 1972 to 2005.

His research was characterised by deep insight and he made pioneering contributions across a wide range of statistical fields. Alastair was acknowledged, in particular, as a world leader in survey sampling theory and the development of methods to efficiently obtain and analyse data from medical studies. His methods are applied in a wide range of areas, notably in public health. Beyond research, he contributed prolifically to the statistical profession in academia, government, and society.

Alastair was a Fellow of the Royal Society of New Zealand, the American Statistical Association, the Institute of Mathematical Statistics, the Royal Statistical Society, and an honorary life member of the New Zealand Statistical Association. In November last year, Alastair was awarded the Royal Society of New Zealand’s Jones Medal, which recognised his lifetime contribution to the mathematical sciences.

Alastair gained his first degrees at the University of Auckland: BSc in Mathematics in 1961 and MSc in Mathematics in 1962. After a period at the New Zealand Department of Scientific and Industrial Research, he pursued a PhD in Statistics at the University of Chicago, graduating in 1965. He then worked at the London School of Economics from 1965-1972.

Alastair returned to New Zealand in 1972 to a post in what was then the Department of Mathematics and Statistics at the University of Auckland; he and wife Margaret had decided that they wanted to raise their children, Andrew and Julie, in New Zealand. Throughout his career, Alastair was regularly offered posts at prestigious universities overseas, but turned them down. However, he held visiting positions at Bell Labs, the universities of North Carolina, Wisconsin, and UC Berkeley in the US, and at the University of Southampton in the UK.

In 1994, the University’s statistics staff, led by Professor George Seber, had a very amicable divorce from the Department of Mathematics and Statistics, and Alastair became the head of the new Department of Statistics. He helped set the tone for the department that still exists – hard-working, but welcoming, and social. The Department of Statistics is now the largest such school in Australasia.

In 2005, Alastair officially retired. A conference in Auckland that year in his honour attracted the largest concentration of first-rank international statisticians in New Zealand in one place at one time. Alastair kept an office in the department and continued writing and advising, coming into work almost every day.

Alastair Scott was an influential teacher and generous mentor to several generations of statisticians who valued his sage advice coupled with his trademark affability. Alastair had a full life professionally and personally. He was a wonderful teacher, mentor, colleague, and friend. We will all miss him greatly and we extend our sincere condolences to Margaret, Andrew and Julie, and his family, friends, and colleagues all over the world.

Team Ratings for Round 14

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 102 matches played, 79 of which were correctly predicted, a success rate of 77.5%.
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.

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 88 matches played, 50 of which were correctly predicted, a success rate of 56.8%.
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.

Q: Isn’t Study suggests we need this first-thing in the morning a perfect example of click-bait?

A: Impressive. And what is this?

Q: This is daylight.

A: Makes sense.  And fits with the picture of someone stretching after getting out of bed.

Q: Does it fit the research?

A: Um.  Not so much. (link)

Q: Not people?

A: No, it was people. It’s just it was light exposure in office buildings.

Q: And these buildings weren’t where people slept?

A: No, that would be potentially inappropriate. It was where they worked.

Q: But giving people more light helped with sleep and depression?

A: “the study did not include a lighting intervention”

Q: So they compared people who had offices with windows and natural light to everyone else?

A: Basically.

Q: And there was a difference in how much sleep they got?

A: No.

Q: In whether they woke up a lot?

A: Not really. The ‘sleep efficiency’ was pretty much the same.

Q: In what, then?

A: In how long they took to fall asleep.

Q: And the depression and stress?

A: Well, the differences were statistically detectable, but they weren’t all that big.

Q: But wouldn’t you expect people with windows in their offices to be happier?

A: Yes. It’s a bit surprising how small the differences were in this study.

Q: So the headline is a bit exaggerated?

A: It’s worse than that. The headline says the research is about what you should have been doing, but it’s actually about what your employer should be doing.

• From the NY Times: In a survey of geographical knowledge and attitudes to North Korea, Americans who can tell their arse from their elbow are more likely to favour diplomacy.  This is different from the Agrabah question, because survey participants aren’t being lied to.

• Perceptions of bias — more precisely, claims about perceptions of bias — are very different between Democrats and Republicans in the US, according to analysis at 538.  Democrats are likely to say they think whites and Christians don’t get discriminated against much but blacks, Muslims, immigrants, gays & lesbians do. For all the groups, about a third of Republicans say they think there’s a lot of discrimination.

• Difficulties with doing randomised experiments on social issues, from the Brookings Institution.  One of the big problems is that there isn’t good theory to allow the results of an experiment to be generalised, in contrast to drug trials where we have a pretty reasonable idea of what it means when a drug does well in a randomised trial population.  A lot of the difficulties do generalise to public health interventions, though. On a related note, economist Noah Smith talks about the role of theory and experiment in economics and in science.

• I wrote last year about judges interrupting each other in the US Supreme Court and whether it depended on gender — the analysis in the media had ignored how much each judge talked.  There’s now an analysis with more variables (and now the right link), and the gender difference looks stronger.

Team Ratings for Round 13

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 94 matches played, 71 of which were correctly predicted, a success rate of 75.5%.
Here are the predictions for last week’s games.

Predictions for Round 13

Here are the predictions for Round 13. 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 80 matches played, 43 of which were correctly predicted, a success rate of 53.8%.
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.

Q: Did you see the Jagerbombs ‘as bad as taking cocaine’ headline in the Herald?

A: Doesn’t sound all that plausible. What’s a Jagerbomb? Is it like a Molotov cocktail?

Q: Apparently it’s Red Bull with Jägermeister.

A: Well, I don’t think I’m in any danger of drinking that.  How did you get the little dotty things over the ‘a’, by the way?

Q: If you hold down the ‘a’ key they pop up as an option (on a Mac). Like the Māori long vowels. But we nearly digress. Is a Jagerbomb really that dangerous?

A: Well, the story goes on to quote the researcher saying “I wondered if they were having a similar impact but to a lesser degree”

Q: And are they?

A: For suitable definitions of ‘same’ and ‘lesser’. And ‘were’.

Q: ಠ_ಠ

A: The research (no link given) looked at whether combining alcohol and energy drinks led to people getting injured more.

Q: That’s not the first thing you think of as a risk of taking cocaine. And how did they do the comparison? Recruit undergraduates with poor taste and give them Jagerbombs?

A: No

Q: You’re not going to say ‘mice’, are you?

A: No, what they did was go to the library and find all the previous studies of alcohol and energy drinks and injury, to review and summarise them.

Q: Is that useful?

A: It can be very useful. You can’t keep all that information in your head even if you’re a qualified Jagerbombologist.  Systematic reviews are a great innovation in modern medical research.

Q: So, how does the risk of injury compare to the risk with cocaine?

A: They didn’t look at that.

Q: Oh. Ok. So how big is the risk?

A: They didn’t come up with anything quantitative, because the previous research studies hadn’t been done in a similar enough way

Q: Did they come up with anything?

A: Yes, the results “suggest support for a relationship between increased risk of injury and [alcohol with energy drink] use”

Q: That’s not all that strong.

A: No.

Q: Was there a stronger relationship than just with alcohol on its own?

A: They say “some studies did not differentiate between injuries occurring in alcohol-only sessions relative to AmED sessions, making a comparison of the risk of injury between alcohol and AmED use impossible.”

Q: Even if there is a difference, couldn’t it be that the sort of people who drink Jagerbombs or rum and Coke are different from people who drink beer, or cosmopolitans, or Sauv Blanc?

A: “Although the results remain mixed in terms of whether impulsivity or risk taking may moderate the relationship between AmED use and injury risk, there is enough evidence to warrant further exploration.”

Q: That all seems very reasonable.

A: The actual story isn’t too bad, either. Just the web-front-page headline.

Q: Wait, doesn’t the headline punctuation imply ‘as bad as taking cocaine’ is a quote? When it totally isn’t?

A: Yes. Yes, it does.