Posts from July 2016 (39)

Public Policy Polling has a history of asking … unusual… questions in their political polls.  For example, asking if you are in favour of bombing Agrabah (the fictional country of Disney’s Aladdin), whether you think Hillary Clinton has ties to Lucifer, and whether you would vote for Harambe (the dead, 17-yr old gorilla) if running as an independent against Trump and Clinton.

From these three questions, the Lucifer one stands out: it comes from a familiar news issue and isn’t based on tricking the respondents. People may not answer honestly, but at least they know roughly what they are being asked and how it’s likely to be understood.  Since they know what they are being asked, it’s possible to interpret the responses in a reasonably straightforward way.

Now, it’s fairly common when asking people (especially teenagers) about drug use to include some non-existent drugs for an estimate of the false-positive response rate.  It’s still pretty clear how to interpret the results: if the name is chosen well, no respondents will have a good-faith belief that they have taken a drug with that name, but they also won’t be confident that it’s a ringer.  You’re not aiming to trick honest respondents; you’re aiming to detect those that aren’t answering honestly.

The Agrabah question is different. There had been extensive media discussion of the question of bombing various ISIS strongholds (eg Raqqa), and this was the only live political question about bombing in the Middle East. Given the context of a serious opinion poll, it would be easy to have a good-faith belief that ‘Agrabah’ was the name of one of these ISIS strongholds and thus to think you were being asked whether bombing ISIS there was a good idea. Because of this potential confusion, we can’t tell what the respondents actually meant — we can be sure they didn’t support bombing a fictional city, but we can’t tell to what extent they were recklessly supporting arbitrary Middle-Eastern bombing versus just being successfully trolled. Because we don’t know what respondents really meant, the results aren’t very useful.

The Harambe question is different again. Harambe is under the age limit for President, from the wrong species, and dead, so what could it even mean for him to be a candidate?  The charitable view might be that Harambe’s 5% should be subtracted from the 8-9% who say they will vote for real, living, human candidates other than Trump and Clinton. On the other hand, that interpretation relies on people not recognising Harambe’s name — on almost everyone not recognising the name, given that we’re talking about 5% of responses.  I can see the attraction of using a control question rather than a half-arsed correction based on historical trends. I just don’t believe the assumptions you’d need for it to work.

Overall, you don’t have to be very cynical to suspect the publicity angle might have some effect on their question choice.

• Public Policy Polling, who were behind the ‘would you bomb Agrabah?’ question last year, are at it again.

 Harambe, as you may recall, is ineligible because of age, vital status, and species.  (/ht @smurray38)

• Nathan Yau at Flowing Data has an animation to illustrate what, say, a 60% chance of winning the US Presidential Election means — for people who don’t work with probabilities regularly, showing them as counts is helpful. Some statisticians would argue that the ‘repeated elections’ way of thinking about the probability is wrong, but that doesn’t affect its usefulness in conveying the number.

• Russell Brown explains numbers and history for Radio NZ’s recent audience success.

• Frances Woolley, a Canadian economist, looks at the recent highly-publicised study examining height trends across the world.  (/ht @BenAtkinsonPhD)

• Wall Street Journal has a lovely glyphmap of US electoral history (/ht @fogonwater)

• Cathy O’Neill writes about the US Computer Fraud and Abuse Act. It criminalises violations of website terms of service — which you’d expect to be a matter of contract law — and puts quite a bit of data journalism at risk.

• Update:  I wrote on how it was strange for an otherwise health 20-year-old law student to be the exemplar patient in a campaign to increase awareness about a disease primarily of the old. Stuff now has a story on who was pushing the publicity campaign.

The ‘ice-bucket’ challenge was intended to raise awareness of the disease ALS and to raise research funds.  Part of this money funded genetic research, and here’s how Stuff describes it, under the headline Ice bucket challenge credited with a medical breakthrough

Researchers have just announced a medical breakthrough. Thanks to the challenge they have identified a gene found to be one of the most common in people with ALS, the deadly disease that affects neurons in the brain and spinal cord.

One News was similarly enthusiastic: Researchers have discovered an important gene linked to Motor Neurone Disease, and it’s all thanks to last year’s viral Ice Bucket Challenge. The story goes on to describe this as ‘paving the way for future treatment’.

Newshub is a little better

The researchers themselves were more restrained:

NEK1 has been previously described as a candidate gene for ALS. Here our findings show that NEK1 in fact constitutes a major ALS-associated gene with risk variants present in ~3% of European and European-American ALS cases.

That is, it’s not new that variants in NEK1 are associated with ALS, and what the research did was confirm this and quantify the extent of association:  about 3% of ALS cases have such a variant.

There’s nothing wrong with the research; this sort of incremental step is how science mostly works, and every bit of information helps when you’ve got a disease with no current cure and a poorly-understood cause. But it’s not a medical breakthrough even for the 3% who have these variants, and there’s no paved road to future treatment.

HealthNewsReview has a longer rant.

Some new headlines:

• Unprecedented Alzheimer’s drug slows disease by 80 per cent 
• Promising Alzheimer’s treatment flops in new trial, crushing hopes 
• Alzheimer’s breakthrough as new pill taken twice a day STOPS disease from shrinking brain
• First drug to halt Alzheimer’s tested by scientists
• Alzheimer’s Maverick TauRx Tries To Weave Success From Failed Trial
• Alzheimer’s Drug LMTX Falters in Final Stage of Trials
• Drug ‘may slow’ Alzheimer’s brain death

Admittedly, the shouty headline is from Daily Mirror, but the other positive ones include the BBC and New Scientist. And, yes, they are talking about the same trial of the same drug.

How can this possibly happen? And who’s right? Here’s the full press release from the conference. It starts off

A clinical trial of LMTM (TauRx Therapeutics, Ltd.) in people with mild to moderate Alzheimer’s failed to demonstrate a treatment benefit in the primary analysis of the full study population in both doses tested. However, in a pre-planned analysis of a small subgroup of the study population that received LMTM as a monotherapy, there was a statistically significant benefit on cognitive and functional outcomes, and slowing of brain atrophy.

The  trial compared two doses of LMTM to placebo, in 891 people, and didn’t find the benefit it was looking for. The press release doesn’t give the results, so we don’t know if there was modest evidence of benefit or basically nothing.

They then compared the 90-odd people who were taking LMTM and no other treatment to the 250-odd who were taking placebo. It’s that relatively small group that has the impressive results.

Reasons behind the negative headlines include

• the regulatory/investment aspect: these results are unlikely to get the drug approved, so TauRx won’t be getting the truckfulls of money they’d be anticipating if the whole trial had been successful
• subgroup analyses are often over-optimistic, because you mainly get to see them when they’re the sole redeeming feature of a disappointing set of results
• in fact, getting positive results in a subgroup isn’t at all unprecedented with Alzheimer’s. Eli Lilly are betting a lot that they’ve found the right subgroup and their drug solanezumab will now be successful.
• it’s unusual to compare people getting LMTM but nothing else with everyone on placebo (rather than people getting placebo but nothing else). You’re not guaranteed a fair comparison by randomisation that way.
• in the other direction, it’s hard to see how other treatments (which focus on stimulating the cells that are still working) would counteract the effect of LMTM (which is trying to prevent protein tangles from forming). But biology is weird, so maybe it’s true.

TL;DR: So, would I try to get this drug if I had an AD diagnosis? It would depend on the actual results in the whole trial (which we aren’t told) and on the details of side effects (which we also aren’t told). But I’d certainly have been disappointed by these results.  And New Scientist should be ashamed of themselves.

David Hood writes at Public Address about his analysis of the NZ Election Survey

The data for the 2014 New Zealand Election Survey was recently released for the general public to make of it what they will, which in the modern world of home data analysis is like parachuting a gazelle into a pride of lions.

Team Ratings for the Semi-finals

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 139 matches played, 101 of which were correctly predicted, a success rate of 72.7%.
Here are the predictions for last week’s games.

Predictions for the Semi-finals

Here are the predictions for the Semi-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 Round 21

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 144 matches played, 91 of which were correctly predicted, a success rate of 63.2%.
Here are the predictions for last week’s games.

Predictions for Round 21

Here are the predictions for Round 21. 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 whinge about NZ papers a lot on StatsChat, and even more about some of the UK stories they reprint. It’s good sometimes to look at some of the UK stories they don’t reprint.  From the Daily Express

The Brexit enthusiast and cabinet Minister John Redwood says “The poll is great news, well done to the Daily Express.” As he seems to be suggesting, you don’t get results like this just by chance — having an online bogus poll on the website of an anti-Europe newspaper is a good start.

(via Antony Unwin)

From Salon: Shock poll: Nate Silver’s election forecast now has Trump winning

That’s not either of his two forecasts, that’s the “now-cast”:

From Nate Silver:

But one method to measure the convention bounce is to look at FiveThirtyEight’s now-cast, our estimate of what would happen in an election held today. We don’t usually spend a lot of time writing about the now-cast because — uhh, breaking news — the election is scheduled for Nov. 8.

Nate Silver’s actual election forecast:

59.5% is low enough to be worrying, but it isn’t less than 40.5%

There’s actually a good story in the Herald about obesity and genetics, based on research in Samoa.  The researchers are interested in finding genetic relationships to understand the biological processes in obesity better. Polynesian peoples are relevant partly because of relatively high obesity rates, but also because each island group was settled by a relatively small number of people, leading to larger genetic differences between nations. It’s the same reason Icelanders are studied a lot by geneticists.

In this study, they found a genetic variant that is essentially non-existent in previously-studied populations (about 1 in 10,000 people) but present in almost half of their sample from Samoa.  People with the variant had, on average, a higher BMI by 1.4 kg/m², which is quite a lot for a genetic effect — at least five times larger than the most important variant previously known, and enough to perhaps be relevant for health. On the other hand, the genetic variant explains only about 1.5% of the variation in BMI between people in the study and less than 10% of the difference in average BMI between, say, Samoa and Japan.

There’s also evidence that the genetic variant has been advantageous to the ancestors of modern Samoans.  Genetic variants that have spread more rapidly through a population tend to have brought along larger chunks of the genome from the person where they first arose.  This shows up as correlation with a larger than usual set of neighbouring variants, which was seen here.  The main reason for a genetic variant to spread more rapidly is if it is beneficial, so that’s probably the explanation.  The story given about survival on long ocean voyages would make sense, but there isn’t any specific genetic evidence for that.

An obvious question is whether this genetic variant is present in other Polynesian populations, perhaps including Māori. No-one knows yet — they haven’t looked, and this is the sort of research where consulting in advance with iwi would be important.