Stats Chat

The Herald had a story and headline based on a bogus online clicky poll today: Covid 19 coronavirus Delta outbreak: Majority vote for South Island alert level change

As we’ve seen in the past, bogus online polls can be very misleading. That last link, for example, compares three bogus polls from the same time period on the same question, whose results differed by more than you’d expect for random samples of only ten people.

The Herald does try to wiggle a bit on interpretation; the story starts “The votes are in and it is clear whether or not Herald readers think the South Island should stay in lockdown after Friday”. But the 70,000-odd votes are a tiny proportion of what the Herald claims as its readership: in January, they reported 610,000 daily print subscribers, 1.9 million monthly unique viewers on the blog, and a weekly ‘brand audience’ of over two million. There’s no reason to expect the poll responses are representative of any of those Herald readerships, either.

Usually one could argue that the bogus polls don’t do any major harm; they just amount to pissing in the swimming pool of public discourse. Usually they don’t get headlines. Usually they aren’t about a sensitive policy question in the middle of a pandemic. If the accuracy of the  numbers matters, you don’t want a bogus poll; if the accuracy doesn’t matter they shouldn’t be the basis for a lockdown-related headline

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.

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.

Team Ratings for Round 24

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 176 matches played, 129 of which were correctly predicted, a success rate of 73.3%.
Here are the predictions for last week’s games.

Predictions for Round 24

Here are the predictions for Round 24. 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 32 matches played, 20 of which were correctly predicted, a success rate of 62.5%.
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 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 29 matches played, 18 of which were correctly predicted, a success rate of 62.1%.
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.

Not news-related, but just an observation from today while I was working on real-time bus data

At 1:30pm, just over 80% of buses were on time (by my fairly stringent metric of all buses; all stops).

That was just before a band of strong wind and moderately heavy rain. Afterwards, at 3:15pm, we’re down to about 70% of buses on time

Update: 4pm: — 53% on time

Rain messes up Auckland traffic, so it will inevitably mess up buses to some extent– bus lanes help, but even with bus lanes, they are affected by other traffic at most intersections.  There isn’t any straightforward solution; making buses allow lots of extra time and take regular naps along the route might fix the on-time metric, but it wouldn’t fix the problem.

PS: The interactive map –when it’s working — is here; the corresponding Wellington one is here

PPS: Bus performance has continued to deteriorate, but now it’s probably down to the likely coming Covid lockdown. Masks on public transport, folks. It’s not just the law, it’s a good idea

Team Ratings for Round 23

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 168 matches played, 123 of which were correctly predicted, a success rate of 73.2%.
Here are the predictions for last week’s games.

Predictions for Round 23

Here are the predictions for Round 23. 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.

Performance So Far

So far there have been 14 matches played, 10 of which were correctly predicted, a success rate of 71.4%.
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 12

I missed predicting Round 11 last week, because of two games being played in the week. Same again this week it seems so I will give predictions for Round 13 after the completion of the Round 12 games.

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 26 matches played, 15 of which were correctly predicted, a success rate of 57.7%.
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: Did you see more than 90% of LGBTQ adults in the US have had the Covid vaccine?

A: How could you even know that?

Q: From Twitter. And! Yahoo! News!

A: But…

Q: It makes sense, right? LGBTQ+ people are less likely to be on the anti-vaccine side of US culture wars, and there’s community experience with health activism

A: But there are queer and trans people in Alabama, not just in San Francisco. And a significant homeless population

Q: But that’s what the survey says

A: Two words: sampling frame

Q: Ok, what’s a sampling frame?

A: It’s the list you work from when you sample people: a list of phone numbers or houses or email addresses or workplaces or whatever. It defines the population you’re going to end up estimating

Q: So they’d just need a list of all the LGBTQ+ people in the US

A:

Q: Ok, yes, that would be scary. How did they really do it?

A: They had a list of some of the LGBTQ+ people in the US (press release, PDF report)

Q: Where did they get the list?

A: “Research participants were recruited through CMI’s proprietary LGBTQ research panel and through our partnerships with over 100 LGBTQ media, events, and organizations.”

Q: That sounds like it might not be very representative

A:  “Because CMI has little control over the sample or response of the widely-distributed LGBTQ Community Survey, we do not profess that the results are representative of the “entire LGBTQ community.””

Q: Exactly.  It might be useful for marketing, but it seems like it’s not going to be representative. They’ll miss some big groups of people

A: “Instead, readers of this report should view results as a market study on LGBTQ community members who interact with LGBTQ media and organizations. CMI views these results as most helpful to readers who want to reach the community through LGBTQ advertising, marketing, events, and sponsorship outreach. Results do not reflect community members who are more closeted or do not interact much with LGBTQ community organizations. More than likely, bisexual community members are also underrepresented in the results.”

Q: When you’re talking in italics like that, does it mean you’re quoting the report?

A: It does. Or the press release

Q: Sounds like they have all the right disclaimers

A: The disclaimers fell off on the way to Yahoo! News! and Twitter, though.