Stats Chat

There’s a story in the Herald arguing for mass vaccination in NZ against group C meningococcal disease.  There’s a good case for the vaccination — it’s a really nasty disease and there aren’t any other good treatment or prevention approaches — but I don’t see how the cost-effectiveness claims in the story can be right.

Dr Gravatt is quoted as saying there would be zero net medical cost for the vaccination program

Dr Gravatt estimated the net cost of vaccinating children at 12 months and again at 18 years would be zero for each “quality-adjusted” year of life saved at a vaccine price of $25 to $40 per dose. The listed prices were around $43 to $87, but discounts would be likely in a bulk contract.

He refers to a British vaccine study — which one isn’t specified.  However, there are cost-effectiveness analyses of the whole British group C meningococcal vaccination program (they vaccinate against group C but not group B, the opposite of NZ).  One, from 2002, estimates  a cost per life year saved of £6259. The second, from 2006, considers a wider range of possible vaccination programs: for the one that’s most similar to what Dr Gravatt proposed it estimates net medical costs of £9082 per quality-adjusted life year, and for the cheapest one, £3653 £2760 (update)per quality-adjusted life year. And that’s assuming the vaccine costs only £12 per dose, and in a country where group C meningococcal disease was slightly more common than it is here.

Another way to look at it: there are about 60000 births per year in NZ, so after the initial catch-up phase we’d be paying for 120000 doses per year. Even at $25 per dose, that comes to $3 million per year. According to the Herald’s story there are about 25 cases per year, so for the vaccination to be cost-neutral even at this lowest suggested price, the average disease case would have to cost the healthcare system $120000. That’s more than ten times what the UK cost-effectiveness study estimated (roughly £4000) including both the immediate cost of treating the disease and the cost of treating the long-term effects.

The vaccine looks to be a lot more cost-effective than, say, the prostate cancer drug that Campbell Live was pushing last week, and because herd immunity is important for this disease, there’s a relatively stronger case for vaccinating everyone, but that would be because the cost is worth it, not because the cost is zero.

Updates, including a lot more technical detail:  (more…)

The Herald has a story on extra-marital affairs (no, not that one), headlined “Men with deep voices sexier, but more likely to cheat – study”

Scientists found that men with masculine, low-pitched voices are better at attracting women – at least those looking for short-term flings.

But the baritone bad boys were also seen as more likely to cheat and not viewed as marriage material.

When you track down the actual research and look at the paper

Women selected lower-pitched men’s voices as more attractive for a short-term relationship (t₈₆ = 6.74, p < .001; M = .70, SD = .279), as more attractive for a long-term relationship (t₈₆ = 5.66, p < .001, M = .67, SD = .277), and as more likely to cheat on their romantic partner (t₈₆ = 5.64, p < .001, M = .68, SD = .298), on a proportion of trials that was significantly greater than chance.

So, firstly, the headline is completely unsupported by the research: there is no information about actual propensity to cheat, just about what women thought about the men based solely on voice recordings.  Second, men with lower-pitched voices were also seen as more attractive, not less attractive, for a long term relationship.

What the research found that’s at least somewhat related to the story is that the advantage of deep voices was smaller in the context of long-term than short-term relationships. The problem is that this sort of difference of differences is quite sensitive to how you summarise your data — a switch from differences to ratios, for example, can easily cause it to reverse.

The story was originally from the Daily Mail. Sex, like cancer, is one of the topics where the Mail is especially untrustworthy

• (Lots) more on the Nobel Prize for Econ, by Dan Davies “So, the Fama/Shiller/Hansen prize, or as the vast majority of comment has it, the prize for “Fama, Shiller and that other guy”. What does it say about the state of economics? I think it encapsulates everything good and bad about the subject.”
• The Herald is treating its clicky webpage poll as headline news again. We’ve seen how inaccurate these polls can be.
• At bit.ly, a real-time map of click-throughs to various media sources (US only, sadly)

From the Medical Journal of Australia

Accurate health journalism helps Australian consumers make informed choices by exposing fraudulent or exaggerated claims about health products and services, by informing them about effective products and services, and by countering disease mongering. A well informed public is also vital to the proper functioning of a modern democracy; and in democratic countries like Australia where the state is a major funder of health services, it is particularly important that the public have accurate information…

While some health reporting in the mainstream media undeniably fails the test of accuracy, it has also been shown that reports about health interventions in the less sensationalist newspapers are more accurate and complete than reports in other media, including online news outlets.

Substitute as necessary for NZ.

(via @vincristine)

Team Ratings for the ITM Cup Finals

Here are the team ratings prior to the ITM Cup Finals, along with the ratings at the start of the season. I have created a brief description of the method I use for predicting rugby games. Go to my Department home page to see this.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

There is a problem with the code I have been using for assessing performance, due to the unusual schedule in the ITM Cup, where some teams play more than one game in a week. I haven’t had time to alter the code so am omitting this section for the time being. Look at last week’s post to see how the predictions went. For the record, there were 6 games correct, out of 8 games played last week

Predictions for the ITM Cup Finals

Here are the predictions for the ITM Cup Finals. 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 the SemiFinals

Here are the team ratings prior to the SemiFinals, along with the ratings at the start of the season. I have created a brief description of the method I use for predicting rugby games. Go to my Department home page to see this.

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, 15 of which were correctly predicted, a success rate of 50%.

Here are the predictions for last week’s games.

Predictions for the SemiFinals

Here are the predictions for the SemiFinals. 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.

• Eric Crampton discusses a Gallup poll in the US which thinks >20% of the population is gay
• At NBR, Horizon polling claims to have predicted the Auckland election most accurately. At least, after they changed which one of their numbers was supposed to be the prediction.  Basically, everyone got the winner right, and getting accurate results has to be pretty much luck given this is only the second election ever for mayor of the supercity.
• From The Civilian, a nice send-up of bogus polls: “Stewart Island to be renamed Harry Styles as a result of online poll”
• Census population counts for areas are now out.  Auckland is bigger. ChCh is only very slightly smaller, and Canterbury is bigger.

Q: There isn’t a Nobel Prize for Mathematics, is there?

A: No

Q: I’ve heard that was because Nobel’s wife was having an affair with a prominent mathematician. Is that true?

A: Almost certainly not

Q: How can you be sure?

A: Various reasons. For a start, Nobel wasn’t married.

Q: Oh. Is there a Nobel Prize for Statistics?

A: No.

Q: Why not?

A: Various reasons. For a start, statistics hadn’t really been invented in 1895, when Nobel died.

Q: Do statisticians ever win Nobel Prizes?

A: Yes and no.

Q: How is that not a simple “yes” or “no”?

A: The Sverige Riksbank Prize in Economic Sciences in Memory of Alfred Nobel has often been given for statistical research. Opinions vary on whether this is a ‘real’ Nobel Prize.

Q: Can you explain how to pronounce that?

A: No.

Q: When was the most recent time it was given for statistics research?

A: Yesterday, to Lars Peter Hansen (together with two other people for non-statistical research)

Q: Can you explain in simple terms what he did?

A: I could try, but Jeff Leek at Simply Statistics has already done a reasonable job

While Ruatara Paapu’s entry was the only nomination last week in our Stat of the Week competition, it is still a worthy winner.

Auckland Councillor Cameron Brown put out a press release entitled: “68% percent [sic] of Aucklanders wanted berm mowing continued”.

However, this statistic is rather misleading – it’s 68% of those who made a submission on berm mowing, not 68% of Aucklanders.

Congratulations Rutara and keep those nominations coming in!

• Mashblock displays the publicly-available Census 2006 data right down to the individual meshblock level 
• The ‘reputation’ component of university rankings seems to favour institutions in cities that people have heard of
• Useful discussion of the Global Innovation Index in the Herald, featuring Shaun Hendy (who now works in the same building as us). I don’t know if the brain drain explanation is true, but it’s the right sort of way to use the data.
• Big Data graphics: cascades of retweeting related to NY Times articles, and click-throughs to the original article