Posts from October 2013 (67)

Sometimes a scientific claim is obviously unreasonable, like when a physicist tells you “No, really, the same electron goes through both slots in this barrier”. You’re all “Wut? No. Can’t be.” They show you the interference pattern. “But did you think of…?” “Yes”. “Couldn’t it be..” “No, we tried that.” “But…”  “And that.”  “Still, what about…?” “That too.” Eventually you give up and accept that the universe is weird. An electron really can go through two holes at once.

On the other hand, sometimes the claim isn’t backed up that well, like when Stuff tells us “Cookies as addictive as cocaine”. For example, while some rats were given Oreo cookies and others were given cocaine, there weren’t any rates who were offered both, so there wasn’t any direct evaluation of preference, let alone of addiction. The cookies weren’t even compared to the same control as the cocaine — cookies were compared to rice cakes, and cocaine-laced water to plain water.

There’s a more detailed take-down on the Guardian site, by an addiction researcher.

Thank you for your nominations in last week’s Stat of the Week competition.

We’ve chosen Michael MacAskill’s nomination of the Christchurch Press article: “Luck of the Irish has sex-disease downside”.

“Irish migrant rebuild workers in Christchurch might or might not have higher rates of sexually transmitted diseases than they did last year.

This story claims that there has been an increase in Irish workers in ChCh with sexually transmitted infections. It doesn’t adjust for the large increase in the total number of Irish workers in the city over the period. No figures are available for other nationalities, so we have no context to judge whether Irish are either over or even under-represented. An absolutely unqualified and uninformed (but sadly, recently re-elected) lay Health Board member is oddly enough asked to contribute his opinion. He prefixes them with the word “Statistically…” to give them more weight. He assumes that all Irish workers in ChCh are heterosexual males, and makes several causal leaps to blame local women for passing on infections.

And why exactly are we just talking about the Irish in the first place?”

There’s also a strong reaction in the comments on that article on Stuff, including someone threatening to complain to the Press Council.

Thanks for alerting us to this article Michael, and congratulations for being our Stat of the Week winner!

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 October 25 2013.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of October 19 – 25 2013 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…)

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

There’s a new edition of the Declaration of Helsinki, the research ethics declaration of the World Medical Association (diffs from the previous version)

Some of the main changes

• Clarification of the principles for research on vulnerable populations, such as developing countries: the question should be relevant to them so that the answer provides benefits to them, and there should be a fair level of other benefits.
• Explicit recognition that risks need to be monitored during the research
• Requiring some way for the treatment identified as best to be available to research participants after a trial
• Adding research sponsors (eg, drug companies) to the list of those with explicit obligations to ensure publication of all results.

(via Alice Dreger and Janet Stemwedel)

• Abraham Lincoln’s “slave map”, via the New Yorker
• The UK Data Explorer. Interactive graphics for UK official data, by James Trimble, who is a computing science student at Glasgow University
• GED VIZ, from the Global Economic Dynamics project in Germany.

• Nature, the well-known science journal, has a new ‘Nature Graphics‘ tumblr with art, infographics, and some actual graphics with information.
• The Herald reports the WHO has listed outdoor air pollution as a leading cause of cancer. They don’t point out that air pollution is going down in most of New Zealand.
• The Herald also has an interesting report of someone getting a deep-vein thrombosis after a long gaming session. Sitting still for long periods has been known to have this risk since WWII, when cases turned up in Britain in air-raid shelters, but the risk is small.  For long plane flights, the risk of death from a blood clot is about one in a million, but more than ten times that many will need hospital treatment.

Anecdotally, many of the New Zealanders I talk to think that a) all American beer is appallingly bad, and that b) this is all that Americans drink. In fact, the US has been leading the micro- and craft- brewing revolution for some years now, and a new survey shows that American beer drinking tastes are changing. Budweiser, the so-called King of Beers, a product of US brewing giant Anheuser Busch, appears to have been deposed by Colorado based Blue Moon Brewing Company. I am sure someone will tell me that far more Budweiser/Millers/Coors is produced than beer from Blue Moon, but hey maybe American’s are just using it to pre-cook bratwursts before grilling like I used to do.

I was a little concerned that this study might be self-selected, or industry motivated, but the information provided gives some reassurance: “Data on behalf Blowfish for Hangovers by a third party, private research firm based on a study of 5,249 Americans who drink alcohol and are over the age of 21. Margin of error for this study is 1.35% at a 95% confidence interval. Additional data on alcoholic beverage sales collected directly by the Alcoholic Epidemiolic Data System (AEDS) from States or provided by beverage industry sources.”

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