Stats Chat

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 38 matches played, 29 of which were correctly predicted, a success rate of 76.3%.
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 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 27 matches played, 18 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Round 8

Here are the predictions for Round 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.

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 September 23 2016.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of September 17 – 23 2016 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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Q: Did you see intelligence is inherited just from mothers?

A: Yeah, nah.

Q: No, seriously. It’s in Stuff. “Recent scientific research suggests that rather than intelligence being genetically inherited from both their parents, it comes from their mother.”

A: I don’t think so.

Q: You’re objecting to their definition of intelligence, aren’t you?

A: Not this time. For today, I’m happy to stipulate to whatever their definition is.

Q: But they have Science! The “intelligence genes originate from the X chromosome” and “Some of these affected genes work only if they come from the mother. If that same gene is inherited from the father, it is deactivated.”

A: That sounds like two different explanations grafted together.

Q: Huh?

A: Some genes are imprinted so the paternal and maternal copies work differently, but that’s got nothing to do with the X chromosome.

Q: Why not?

A: Because any given cell has only one functioning X chromosome: for men, it comes from your mother, for women, it’s a random choice between the ones from each parent.

Q: Ok. But are all the intelligence genes on the X chromosome?

A: No. In fact, modern studies using hundreds of thousands of genetic variants suggest that genes contributing to intelligence are everywhere on the genome.

Q: But what about the ‘recent research’?

A: What recent research? I don’t see any links

Q: Maybe they’re in the blog post that the story mentions but doesn’t link to. Can you find it?

A: Yes.

Q: And the references?

A: Mostly in mice.

Q: But there’s one about a study in Glasgow, Scotland. In nearly 13,000 people.

A: There is, though it’s actually an analysis of the US National Longitudinal Study of Youth.  Which, strangely enough, did not recruit from Glasgow, Scotland. And less than half of the 12,686 participants ended up in the analysis.

Q: Whatever. It’s still recent research?

A: Ish. 2006.

Q: And it found mother’s intelligence was the most important predictor of child’s intelligence, though?

A: Yes, of the ones they looked at.

Q: So, more important than father’s intelligence?

A: That wasn’t one of the ones they looked at.

Q: “Wasn’t one of the ones they looked at”

A: Nope.

Q: Ok. So is there any reason for saying intelligence genes are on the X chromosome or is it all bollocks?

A: Both.

Q: ಠ_ಠ

A: Especially before modern genomics, it was much easier to find out about the effects of genes on the X chromosome, since breaking them will often cause fairly dramatic disorders in male children.

Q: So it’s not that more intelligence-related genes are on the X chromosome, just that we know more about them?

A: That could easily be the case. And just because a gene affects intelligence when it’s broken doesn’t necessarily mean small variations it in affect normal intelligence.

Q: But wouldn’t be it great if we could show those pretentious ‘genius’ sperm-donor organisations were all useless wankers?

A: On the other hand, we don’t need more reasons to blame mothers for their kids’ health and wellbeing.

Since we have another episode of democracy coming on, there are starting to be more stories about polls for me to talk about.

First, the term “bogus”.  Two people, at least one of whom should have known better, have described poll results they don’t like as “bogus” recently. Andrew Little used the term about a One News/Colmar Brunton poll, and Nick Leggett said “If you want the definition of a bogus poll this is it” about results from Community Engagement Ltd.

As one of the primary NZ users of the term ‘bogus poll’ I want it to mean something. Bogus polls are polls that aren’t doing anything to get the right answer. For example, in the same Dominion Post story, Jo Coughlan mentioned

“…two independent Fairfax online Stuff polls of 16,000 and 3200 respondents showing me a clear winner on 35 per cent and 50 per cent respectively.”

Those are bogus polls.

So, what about the two Wellington polls cited as support for the candidates who sponsored them? Curia gives more detail than the Dominion Post.  The results differ by more than the internal margin of error, which will be partly because the target populations are different (‘likely voter’ vs ‘eligible’), and partly because the usual difficulties of sampling are made worse by trying to restrict to Wellington.

It wouldn’t be unreasonable to downweight the poll from Community Engagement Ltd just because seem to be a new company, but the polls agree the vote will go to preferences. That’s when things get tricky.

Local elections in NZ use Single Transferable Vote, so second and later preferences can matter a lot.  It’s hard to do good polling in STV elections even in places like Australia where there’s high turnout and almost everything really depends on the ‘two-party preferred’ vote — whether you rank Labor above or below the L/NP coalition.  It’s really hard when you have more than two plausible candidates, and a lot of ‘undecided’ voters, and a really low expected turnout.

With first-past-the-post voting the sort of posturing the candidates are doing would be important — you need to convince your potential supporters that they won’t be wasting their vote.  With STV, votes for minor candidates aren’t wasted and you should typically just vote your actual preferences, and if you don’t understand how this works (or if think you do and are wrong) you should go read Graeme Edgeler on how to vote STV.

• From the Yorkshire Ranter: simple explanations of Brexit that aren’t supported by the data

• From Cardiogram: using the Apple Watch to diagnose abnormal heart rhythms

• From MIT Technology Review, an analysis of emotional patterns in fiction. “We find a set of six core trajectories which form the building blocks of complex narratives” They don’t really cover the possibility that they find six just because that’s as many as they can align neatly with their current approach..

• A reminder from the last US elections: ‘momentum’ doesn’t mean anything with votes — it’s a metaphor, not an analogy.

• From Hilda Bastian: The quality of a research study is rarely uniformly good across all the things it studies (though it could be uniformly bogus)

• On diagnosing depression from Instagram photos “But they’ve buried the real story. The depression rate among adults in the United States is 6.7%. The depression rate among the crowdsourced workers who shared their photos is 41.2%” (Medium)

Team Ratings for Finals Week 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.

Performance So Far

So far there have been 196 matches played, 126 of which were correctly predicted, a success rate of 64.3%.
Here are the predictions for last week’s games.

Predictions for Finals Week 2

Here are the predictions for Finals Week 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 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 30 matches played, 24 of which were correctly predicted, a success rate of 80%.
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.

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 23 matches played, 15 of which were correctly predicted, a success rate of 65.2%.
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.

I wrote last week about the importance of links.  Having links doesn’t guarantee the claims are justified, but it does make it a lot easier to check.  As an exhibit, consider today’s Stuff story about “Healing Foods for Spring Allergies“, which has lots of links.

• Garlic, we are told “has incredible antibiotic properties that can help clear mucous and fight infection.” There are two links. One is to a review article that summarise a lot of lab studies of allicin, a chemical in garlic.  These studies did not involve anyone, even mice, eating garlic — the chemical was applied directly to bacteria growing in Petri dishes.  The other is a review of a much wider set of studies of garlic and garlic extracts. Again, the studies are almost all in vitro, that is, “in lab glassware”.  This one contains the sentence “However, claims of effectiveness of garlic on common cold appear to rely largely on poor quality evidence”. And there’s nothing that even purports to be slightly related to “spring allergies”

• Vitamin C is supposed to be an “effective anti-histamine”.  The link to “clinical trials” refers to two studies in 1992, actually in people and published in real journals — though not available online through the journals’ websites.  However, the abstract of one of them is easily available online. It isn’t a clinical trial — it’s an uncontrolled before-after experimental study in healthy people — and they didn’t find the effect of vitamin C they were actually looking for.The other one was harder to find, and I don’t have an open-access source. It also wasn’t a clinical trial: it was an experiment in nine healthy  university students.  They started off getting 500mg/day of vitamin C — a level that could be achieved by a well-chosen diet — and then were escalated to 2000mg/day. There was no effect on blood histamine levels from 500mg/day, but a 40% lowering with 2000mg/day.  On the other hand “At the end of the third week of the study, two participants withdrew complaining of chronic diarrhea. Another reported diarrhea but completed the study. Osmotic diarrhea is considered the only major side effect of taking large doses of vitamin C (15). After several days at the 2,000-mg dosage level, two participants complained of dry nose and nosebleeds. Their dosage level was reduced to 1,000 mg daily and they completed the study without further complications. According to a document (JPI-HS-103-2) prepared in May 1991 by Janssen Pharmaceuticals of Piscataway, NJ, dryness of the eye, ear, nose, and throat is a common side effect of antihistamine drugs.” And, again, they didn’t even look at allergy symptoms.

• “If you suffer from sinus inflammation, pineapple is the fruit for you.”  The link is to a review of studies of pineapple extract for arthritis. Sinus inflammation is not mentioned.  Even for arthritis, the article says “The data available at present indicate the need for trials to establish the efficacy and optimum dosage for bromelain and the need for adequate prospective adverse event monitoring in such chronic conditions as osteoarthritis.”

• “Gargling salt water has recently been shown to help prevent upper respiratory infections in healthy people.” That’s quite a good study, but it compared plain water to water with povidone/iodine antiseptic.  It’s quite plausible that salt water also works, but the research didn’t show it.

• “Chicken soup is a wives’ tale with substance!”.  There are two links. One is to Mercola.com, and so isn’t going to be useful.  The other is to an in vitro study of mixing chicken soup extracts with neutrophils, a particular type of immune-related white blood cell.  It might be relevant if you were going to stick the chicken soup up your nose instead of drinking it.

There’s nothing wrong with these foods from a health point of view. I like chicken soup, although I prefer it with lemongrass, lime, and chili. But you’d expect the links to be to the strongest evidence available. And the disappointing thing is, they might well be.