Posts from July 2019 (13)

Team Ratings for Round 20

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 144 matches played, 91 of which were correctly predicted, a success rate of 63.2%.
Here are the predictions for last week’s games.

Predictions for Round 20

Here are the predictions for Round 20. 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 4

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.

Note that Cheetahs2 refers to the Cheetahs team when there is a Pro14 match. The assumption is that the team playing in the Pro14 is the top team and the Currie Cup team is essentially a second team. Possibly there will be no such clashes this year

Performance So Far

So far there have been 9 matches played, 6 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Round 4

Here are the predictions for Round 4. 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 story at the  Huffington Post, based on a new research paper, saying

Genes account for about 80% of a child’s risk of developing autism, a massive new study finds.

That link is not from the HuffPost story (they don’t link), but via Spectrum News, whose story is similar except they actually use the word “heritability” in a few places.

The abstract of the research paper says

Based on population data from 5 countries, the heritability of ASD was estimated to be approximately 80%, indicating that the variation in ASD occurrence in the population is mostly owing to inherited genetic influences, with no support for contribution from maternal effects.

so this is a case where the claims come from the scientists — but where the claims aren’t as strong before you translate them from Science to English.

If you think about it for a few minutes, it obviously can’t be true in a straightforward sense that 80% of the risk of developing autism is genetic(or, more precisely of being diagnosed with it, since that’s what can be measured).  Autism (diagnosis) is much more common than it used to be. For example, the US Centers for Disease Control report that from 2000 to 2014, “ASD prevalence estimates increased from 6.7 to 16.8 per 1,000 children aged 8 years, an increase of approximately 150%.” Absolutely none of this change is genetic: fourteen years isn’t long enough for population genetic changes. In the US, over that period, something non-genetic that varies with time was responsible for the majority of the autism (diagnosis) risk.  Improvements in diagnosis are probably one contributing factor.

Heritability is an important technical measure that sounds more interesting than it actually is.  It’s related to whether things are genetically determined, but it isn’t the same. For example, in humans, “number of legs” has very low heritability, but the reason nearly everyone has two legs is genetic.

More seriously, suppose that a condition requires both that you have a particular genetic variant and that you experience a particular environmental exposure.  Whether the condition ‘looks’ genetic or environmental will depend on who you compare.  If you compare among people of northern European ancestry living in NZ, melanoma skin cancer looks to be mostly environmental: it’s caused by sunburn.  If you compare among people living in South Africa, melanoma looks substantially genetic: it’s caused by a lack of melanin in the skin, and the genetic contributions to skin colour are moderately well understood.

Team Ratings for Round 19

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 136 matches played, 85 of which were correctly predicted, a success rate of 62.5%.
Here are the predictions for last week’s games.

Predictions for Round 19

Here are the predictions for Round 19. 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 3

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.

Note that Cheetahs2 refers to the Cheetahs team when there is a Pro14 match. The assumption is that the team playing in the Pro14 is the top team and the Currie Cup team is essentially a second team. Possibly there will be no such clashes this year

Performance So Far

So far there have been 6 matches played, 4 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Round 3

Here are the predictions for Round 3. 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 18

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 128 matches played, 77 of which were correctly predicted, a success rate of 60.2%.
Here are the predictions for last week’s games.

Predictions for Round 18

Here are the predictions for Round 18. 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 2

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.

Note that Cheetahs2 refers to the Cheetahs team when there is a Pro14 match. The assumption is that the team playing in the Pro14 is the top team and the Currie Cup team is essentially a second team. Possibly there will be no such clashes this year.

Performance So Far

So far there have been 3 matches played, 2 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Round 2

Here are the predictions for Round 2. 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 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.

Note that Cheetahs2 refers to the Cheetahs team when there is a Pro14 match. The assumption is that the team playing in the Pro14 is the top team and the Currie Cup team is essentially a second team. Possibly there will be no such clashes this year.

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.

• AI Ethics: Seven Traps, from freedom-to-tinker
• The NZ$ Herald has a front page story about over-screening for eye conditions, which uses the wonderful word “incidentaloma” (an unnecessary and accidental diagnostic finding)
• On the avocado-toast libel of millennials: actually millennials earn more money, and spend less on food and entertainment than the baby boomers did at the same age (inflation-adjusted)
• Lisa Charlotte Rost looks at an Economist graphic about unprecedented Arctic ice melting and redraws it so it’s true.
• In a new podcast by The Spinoff, Russell Brown talks to two AI/algorithm experts about what ‘algorithms’ are.
• A widely-publicised study of gut bacteria and autism in mice has problems. I’m quoted not believing the statistical analysis.
• From the Sydney Morning Herald, a graphic depicting the size of a blue whale in terms of more familiar, everyday objects (though the typical adult blue whale is a few metres shorter than that)
  

From Sky News and ABC News and the Guardian

Four out of five people identified by the Metropolitan Police’s facial recognition technology as possible suspects are innocent, according to an independent report.

The Police prefer a different definition of accuracy that says the error rate is about 1 in 1000.  It’s not surprising they prefer to say the error rate is 1 in 1000, but you might wonder how you can get two definitions that different.

The full report is here (PDF). In a set of trials in UK cities, the system identified 42 matches to people on the watchlists.  Of these, 8 were confirmed as correct, 16 were identified as wrong just by looking at the pictures, 14 were identified as wrong by checking id, and for 4 of the matches the police couldn’t find the person to check their id.  If you’re feeling really generous you could say the police would be just as good at discarding poor matches in real life as they are in a carefully audited field trial, and you might then say you had 8 right, 14 wrong, and 4 “don’t know” in cases where the police were convinced enough to go up to someone and ask for id; that’s still not 50%.

The Police definition of error rate is the number of errors as a fraction of all the faces scanned.  If you make 14 or 18 or 34 errors in scanning tens of thousands of faces, the error rate per face scanned will be low.  The problem is that, under this definition, the error rate of just not using the facial recognition software is even lower than the 1 in 1000 from using it.

What the stories don’t really do is ask what the error rate should be? The right answer would need to combine the harm done by false matches and the benefit from true matches.  One might also want to consider the benefits from deterring crime or the harm from giving the police more pretexts to challenge people they didn’t like.   In medicine we tolerate screening tests that have error rates worse than this facial recognition system — but in situations where people give consent to be screened and to any further follow-up.

It’s hard to answer the question of what error rate would be ok, but it’s important to ask it.