Posts from May 2015 (43)

Team Ratings for Round 15

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, 60 of which were correctly predicted, a success rate of 65.2%.

Here are the predictions for last week’s games.

Predictions for Round 15

Here are the predictions for Round 15. 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 the MetService warnings page

The ‘confidence’ levels are given numerically on the webpage as 1 in 5 for ‘Low’, 2 in 5 for ‘Moderate’ and 3 in 5 for ‘High’. I don’t know how well calibrated these are, but it’s a sensible way of indicating uncertainty.  I think the hand-drawn look of the map also helps emphasise the imprecision of forecasts.

(via Cate Macinnis-Ng on Twitter)

Each week, we would like to invite readers of Stats Chat to submit nominations for our Stat of the Week competition and be in with the chance to win an iTunes voucher.

Here’s how it works:

• Anyone may add a comment on this post to nominate their Stat of the Week candidate before midday Friday May 22 2015.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of May 16 – 22 2015 inclusive.
• Quote the statistic, when and where it was published and tell us why it should be our Stat of the Week.

Next Monday at midday we’ll announce the winner of this week’s Stat of the Week competition, and start a new one.

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If you’d like to comment on or debate any of this week’s Stat of the Week nominations, please do so below!

Part One: Affiliation and pragmatics

The US firm Public Policy Polling released a survey of (likely) US Republican primary voters last week.  This firm has a habit of including the occasional question that some people would consider ‘interesting context’ and others would call ‘trolling the respondents.’

This time it was a reference to the conspiracy theory about the Jade Helm military exercises in Texas: “Do you think that the Government is trying to take over Texas or not?”

32% of respondents said “Yes”. 28% said “Not sure”. Less than half were confident there wasn’t an attempt to take over Texas. There doesn’t seem to be widespread actual belief in the annexation theory, in the sense that no-one is doing anything to prepare for or prevent it. We can be pretty sure that most of the 60% were not telling the truth. Their answer was an expression of affiliation rather than an accurate reflection of their beliefs. That sort of thing can be problem for polling.

Part Two: Mode effects and social pressure

The American Association for Public Opinion Research is having their annual conference, so there’s new and exciting survey research coming out (to the extent that ‘new and exciting survey research’ isn’t an oxymoron). The Pew Research Center took two random groups of 1500 people from one of their panels and asked one group questions over the phone and the other group the same questions on a web form.  For most questions the two groups agreed pretty well: not much more difference than you’d expect from random sampling variability. For some questions, the differences were big:

It’s not possible to tell from these data which set of answers is more accurate, but the belief in the field is that people give more honest answers to computers than to other people.

As I’ve commented before, most good-quality randomised trials of vitamins in humans have disappointing results. A few don’t, and it’s nice to see these reported accurately.  The Herald tells us about an  Australian trial which has found nicotinamide, a version of vitamin B3, can reduce the rate of new minor skin cancers in people who already have had a lot of them.  This isn’t especially dramatic, but for many older pale-skinned people in New Zealand, Australia, or South Africa it could reduce a recurrent medical annoyance.

The only real omission in the Herald story is the link to the research: there’s a conference abstract for a talk to be given at the American Society for Clinical Oncology conference later this month.

Update: yes, this sort of story is less impressive and has less public health significance than claiming WiFi causes brain cancer in children, but it does have the advantage of being true.

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 72 matches played, 38 of which were correctly predicted, a success rate of 52.8%.

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 86 matches played, 55 of which were correctly predicted, a success rate of 64%.

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.

• Rating systems are the popular way to scale ‘reputation’ statistically so it works for internet transactions between people who don’t know each other. Tom Slee has a couple of pieces (via Cosma Shalizi): Some Obvious Things About Internet Reputation Systems  and In praise of fake reviews:So the reviews that a restaurant owner believes are most likely to be fair are precisely the ones that Yelp judges to be untrustworthy….Unfortunately for restaurateurs, their opinions on trustworthy reviews are irrelevant. The company is not legally bound to be fair in its filtering and sorting activities,
• Another example of interesting results failing to replicate, this time from a popular TED talk about posture. As the post at Data Colada points out, this is a strong non-replication: it’s not just that they didn’t see they effect, they ruled out even much weaker effects. There’s a reason statisticians go on and on about over-interpretation of single, small studies.
  
• Looking at the Census data on religion, a map and set of stories from Lincoln Tan and Harkanwal Singh at the Herald

• A rather different form of data journalism, reported at Buzzfeed (or the original paper report here). The Telegraph had a ‘tactical voting tool’ that said who you should vote for if your goal was a Labour or Tory government.  It was mostly honest, despite the paper’s well-known preferences. However, as Buzzfeed’s headline says: “The Telegraph’s Tactical Voting Tool Was Coded To Never Recommend The SNP”

• From the LA Times, Wylie Burke on “Why whole-genome testing hurts more than it helps” (disclosure: I once co-supervised a student with Prof Burke)

• A Slate article by a lawyer says Wyoming has ‘criminalized citizen science’ by creating a law against collecting and reporting environmental data. Now, Wyoming has created crimes of “unlawful collection of resource data” and “trespassing to unlawfully collect resource data”, but I’m pretty sure the Slate article exaggerates them.  “Unlawful collection” can only happen on private land, which the article clearly gets wrong. “Trespassing to unlawfully collect” can happen on public land, but I’m not convinced that in the National Park example there isn’t the necessary authorisation to enter the land. Presumably the law does something or they wouldn’t have bothered passing it, and it’s probably something evil, but a better article would have been nice.

Each week, we would like to invite readers of Stats Chat to submit nominations for our Stat of the Week competition and be in with the chance to win an iTunes voucher.

Here’s how it works:

• Anyone may add a comment on this post to nominate their Stat of the Week candidate before midday Friday May 15 2015.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of May 9 – 15 2015 inclusive.
• Quote the statistic, when and where it was published and tell us why it should be our Stat of the Week.

Next Monday at midday we’ll announce the winner of this week’s Stat of the Week competition, and start a new one.

(more…)