Archives (240)

COViD edition:

• T-cells. Recent research has found some people already have a T-cell immune response to the COViD virus — in some cases due to getting SARS Classic,  nearly two decade ago, and in some cases probably from animal coronaviruses. That’s encouraging for the prospects  of a vaccine.  But in the  US there are people saying this means those people are immune and we’re near the herd immunity threshold.  That’s completely untrue. The infectiousness of the virus was estimated from how fast it spreads in real populations — so if 50% of people are immune, that just means the virus is twice as infectious as we thought, and the herd immunity threshold is higher.
• T-cells: Some people have T-cell responses already, but we don’t actually know those people are immune, or even less susceptible. As Ed Yong explains “Immunology is where intuition goes to die“
• If you want to know about vaccine candidates for COVID: first, read the introduction by Siouxsie Wiles and Toby Morris, then look at the blogs of Hilda Bastian and Derek Lowe. Hilda is an expert on evidence in health and started out as a healthcare consumer advocate. Derek  is a pharmaceutical chemist.
• What is genome sequencing for the virus and why? Basic introduction from Siouxsie and Toby at The Spinoff, more from David Welch’s op ed at Stuff
• Why we need randomised trials: The Mayo Clinic, in the US, has given plasma from recovered COVID cases to more than 35,000 people and they still don’t really know if it works.
• And now for something completely different: there’s an IMDB entry for the 1pm Covid Briefing, and reviews of season 2 are starting to stream in.

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 78 matches played, 52 of which were correctly predicted, a success rate of 66.7%.
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.

From NewsHub: Coronavirus: New test might detect COVID-19 in just a second, doesn’t involve nose swab.

They get points for a less positive headline than the Reuters original, but

The center said in an initial clinical trial involving hundreds of patients, the new artificial intelligence-based device identified evidence of the virus in the body at a 95 percent success rate.

As far as I can tell, the claim comes entirely from a press release — I haven’t been able to find any more data. What this implies is that Reuters (and NewsHub) don’t have any way to know what “a 95% success rate” actually means.

A COViD test can be wrong in two ways: it can miss actual infections or it can think there’s an infection when there isn’t.  In the New Zealand context, missing only 5% of infections would be doing well.  Thinking 5% of healthy people are infected would make the test useless. We’ve done roughly 500,000 COVID tests so far in New Zealand. If 5% were false positives, that would be 25,000 people incorrectly thought to be cases.

Also, it matters a lot when people are tested, and for what reason. Someone who is currently sick is  more likely to test positive than someone who is  infected but has not developed symptoms.  An initial clinical study will usually involve people whose infection status is known, leaving out  the more important and more difficult cases.

To be fair to the journalists, there’s expert comment in the story that makes some of these points

The amount of virus present in saliva increases as patients get sicker, he said, and a big challenge is to detect in “people who are borderline”.

“It will be a game changer only if we see validation of this technology against the current technology,” he said.

It might also be worth noting that the researcher in  question, Dr Eli Schwarz, has a previous example of overly-optimistic press releases during the pandemic. He is running a trial of the anti-parasite drug ivermectin, describing it as a possible cure.  Unfortunately, the Australian lab experiment that is said to support ivermectin use found that the drug destroyed the virus only at concentrations nearly five orders of magnitude higher than those being used in the trial.

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 12 matches played, 9 of which were correctly predicted, a success rate of 75%.
Here are the predictions for last week’s games.

Please note that if you are checking back on my predictions, there is a different prediction of the points difference for the Rebels versus Brumbies game. I had not realised this was to be played at a neutral ground so gave the Rebels home ground advantage. I still had the Brumbies as winning so I still had the result wrong. I have changed the prediction now so I don’t mess up my ratings for future games.

At the moment it requires an amount of checking to ensure I have home ground advantage assignments correct in games played in Australia. That is particularly the case in the NRL with games played in Sydney.

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 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 18 matches played, 13 of which were correctly predicted, a success rate of 72.2%.
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 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 104 matches played, 70 of which were correctly predicted, a success rate of 67.3%.
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.

• Newshub has a story about so-called ‘lucky’ Lotto stores.  I’ll recycle a previous response.
• The Productivity Commission are arguing that the extra week in lockdown was unnecessary and very expensive. Their analysis is wrong; it does not seem to consider whether and how much the extra week reduced the risk of needing a second lockdown, which was part of the reason for doing in.  I’m not saying the extra week was the right decision — you can’t tell, without modelling the extra risk, which they didn’t do.  It’s like saying insurance is not cost-effective because your house didn’t burn done. Insurance may or may not be cost-effective, but that isn’t how you tell.
• Ed Yong at the Atlantic, on why there’s so much we don’t know about COVID immune response: Immunology Is Where Intuition Goes to Die
• The Human Gene Nomenclature Committee has changed the names of a bunch of genes. Not because they’re named after unpleasant historical figures, but because Excel keeps trying to turn them into dates:  SEPT1, OCT4, MARCH1.  Spreadsheets are useful (and Excel is the world’s most popular statistical software), but you do need to keep a sharp eye on them
• Newshub reports on an attempt to get Pharmac to pay for a drug that costs half a million dollars per patient per year.  I’ll outsource the basic statistical comparison to Matt Nippert on Twitter — the total cost would be about a quarter of Pharmac’s budget (and I’ll just note that this is slightly more than it spends on cancer.)
• If you thought our Census had problems, look at the US.  The American Statistical Association and the American Association for Public Opinion Research are among the groups who want the data collection extended rather than shortened.

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 10 matches played, 9 of which were correctly predicted, a success rate of 90%.
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 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 16 matches played, 11 of which were correctly predicted, a success rate of 68.8%.
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 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 96 matches played, 64 of which were correctly predicted, a success rate of 66.7%.
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.