Stats Chat

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 24 matches played, 15 of which were correctly predicted, a success rate of 62.5%.
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.

Turnitin, a company that looks for similar word sequences in student assignments, says that it can now detect ChatGPT writing.  (Stuff, RNZ)

The company is 98% confident it can spot when students use ChatGPT and other AI writing tools in their work, Turnitin’s Asia Pacific vice president James Thorley said.

“We’re under 1% in terms of false positive rate,” he said.

It’s worth looking at what that 1% actually means.  It appears to mean that of material they tested that was genuinely written by students, only 1% was classified as being written by ChatGPT.  This sounds pretty good, and it’s a substantial achievement if it’s true. This doesn’t mean that only 1% of accusations from the system are wrong. The proportion of false accusations will depend on how many students are really using ChatGPT. If none of them are, 100% of accusations will be false; if all of them are, 100% of accusations will be true.

What does the 1% rate mean for a typical student?  An average student might hand in 4 assignments per course, for 4 courses per semester, two semesters per year.  That’s nearly 100 assignments in a three-year degree.  A false accusation rate of 1 in 100 means an average of one false accusation for each innocent student, which doesn’t sound quite as satisfactory.

The average is likely to be misleading, though.  Some people will be more likely than others to be accused.  In addition to knowing the overall false positive rate, we’d want to know the false positive rate for important groups of students.  Does using a translator app on text you wrote in another language make you more likely to get flagged? Using a grammar checker? Speaking Kiwi? Are people who use semicolons safe?

Turnitin emphasize, as they do with plagiarism, that they don’t want to be blamed for any mistakes — that all their tools do is raise questions.  For plagiarism, that’s a reasonable argument.  The tool shows you which words match, and you can then look at other evidence for or against copying. Maybe the words are largely boilerplate. Maybe they are properly attributed, so there is copying but not plagiarism.  In the other direction, maybe there are text similarities beyond exact word matches, or there are matching errors — both papers think Louis Armstrong was the first man on the moon, or something.  With ChatGPT there’s none of this. It’s hard to look for additional evidence in the text, since there is no real way to know whether something you see is additional or is part of the evidence that Turnitin already used.

• How to win at roulette. No, they haven’t repealed the martingale optional stopping theorem, but no mathematical model is a perfect description of reality
• Farah Hancock has a good series of reports about Auckland and Wellington buses, for Radio NZ.
• “At the outset, it’s important to note that the finding that “exercise is better than medicine” for depression is one that you cannot possibly make from this paper, because the authors *literally excluded papers that compared exercise to medication*” — a Twitter thread on claims about a new study
• Riding an electric bike drops heart and cancer risks, finds German study. Except it doesn’t.  The published German study compares exercise levels and accident rates of a group of people riding electric and acoustic bikes. That’s all it does. Unsurprisingly, it finds that the e-bikers still get exercise, but not quite as much as the people using traditional bicycles.  There’s a lot of claims of evidence of major  health effects, that the researchers are supposed to have described to Der Spiegel (I don’t subscribe, so I can’t check).  These are (a) unpublished, and (b) can’t be as described — the study included about 2000 reasonably healthy participants and ran for twelve months, so it can’t possibly have collected substantial evidence about prevention of cancer or Alzheimer’s or heart disease.  That’s before we even get to any issues about confounding: how much does your health affect cycling vs cycling affecting your health.  As a long-term e-cyclist, I’d love these claims to be based on convincing evidence, but they just aren’t.
• Via David Rumsey on Twitter, the first ‘flow’ visualisation maps, from the 1838 Irish Railway Commission Atlas
• 
• From Kieran Healy, the relationship between height and number of points scored in the US professional basketball league. No, there isn’t a visually clear relationship. That’s because you’re selecting everyone for being very good at basketball, and the shorter guys need to be better in other ways to compensate.  Height obviously matters; other things matter too.  In the same ways, using some sort of standardised test as a criterion for university admission will make it look as if the test isn’t related to performance at university.
  

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 48 matches played, 25 of which were correctly predicted, a success rate of 52.1%.
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.

Team Ratings for Week 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 40 matches played, 31 of which were correctly predicted, a success rate of 77.5%.
Here are the predictions for last week’s games.

Predictions for Week 8

Here are the predictions for Week 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.

Team Ratings for Round 6

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 20 matches played, 12 of which were correctly predicted, a success rate of 60%.
Here are the predictions for last week’s games.

Predictions for Round 6

Here are the predictions for Round 6. 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 6

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 40 matches played, 20 of which were correctly predicted, a success rate of 50%.
Here are the predictions for last week’s games.

Predictions for Round 6

Here are the predictions for Round 6. 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 Week 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 Week 7

Here are the predictions for Week 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.

Team Ratings for Round 5

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 16 matches played, 9 of which were correctly predicted, a success rate of 56.2%.
Here are the predictions for last week’s games.

Predictions for Round 5

Here are the predictions for Round 5. 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.

I was not aware the Currie Cup was starting, and only just saw the results recently. Sorry that I missed the first three rounds: I had always intended to give predictions for it this year again.

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.

Performance So Far

So far there have been 12 matches played, 9 of which were correctly predicted, a success rate of 75%.
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.