Posts filed under General (3148)

NewsHub and Radio NZ had stories about New Zealand blackcurrant juice and its claimed ability to make exercise less tiring

Scientists at Plant & Food Research have found that juice from New Zealand blackcurrants consumed prior to exercising could increase motivation to adhere to exercise.

and

Plant and Food science group leader, Dr Roger Hurst says New Zealand blackcurrants are high in the properties, which help your body recover from exercise. He also said polyphenol lifted mood, so that people felt more inclined to exercise better and for longer.

The open-access research paper is here, and the press release is here. It was a placebo-controlled randomised experiment, which is good. Even better, it was pre-registered at the ANZ Clinical Trials Registry, so we can tell what the researchers said they planned to do and match that up to what they say they have done.

Participants drank real or fake blackcurrant juice before a long period of gentle walking on a treadmill.  People who drank real blackcurrant juice felt better (by about half a point on a ten-point mood scale) and felt they were exerting themselves less (by about one point on a twenty-point scale). That’s all as the stories claim.  The researchers also found a bunch of biochemical things that were consistent with what they expected.

The main critical thing I’d say is that the study registration listed the effect on exercise duration as the first primary endpoint; that is, the main question the study was about.  There was no real evidence of any effect on exercise duration, and this negative finding for the primary study question has been rather deemphasised in the press release and media coverage. The research paper does give the exercise results, but doesn’t mention their status as a primary endpoint — I wouldn’t have known if I hadn’t looked up the study pre-registration, and I might well have assumed this was a small preliminary study that wasn’t really expecting to find exercise differences.

Which, of course, is why pre-registration is so helpful.

I make a lot of fuss about the media not linking to scientific papers. So do many other people who write about science.  This isn’t just a weird kink: part of what makes it science is that you can find out what the researchers did and why.

Usually the lack of links is because the journalist doesn’t put them in.  Today, we have two other cases, in sort of opposite directions.

First, the world’s largest ex-parrot. According to a lot of new stories, especially in the UK, there is a newly discovered giant dead parrot from central Otago. It stood a metre high. Some of the more excitable stories claim it was a cannibal, but that seems to be because they have ‘cannibal’ and ‘carnivore’ (or ‘omnivore’) confused.   Many of the stories give a link to a research paper in the Royal Society’s journal Biological Letters. The link doesn’t work. The most likely explanation is that the journal just hasn’t got around to publishing the paper yet, and the link will start working in a day or two.  But it’s still not good science practice or science publishing to deliberately work up news stories about research that isn’t available to read.

Second, there’s a story on Stuff about a company claiming to use epigenetics to personalise health advice.  I say ‘claiming’ because (a) the company doesn’t actually measure any epigenetics, and (b) there isn’t any evidence that I (or the outside expert quoted in the story) know of that says it works to customise health advice using epigenetics.   The health advice is quite likely perfectly sensible and beneficial to its customers. And if a company wants to use head measurements as well as height and weight to say how you should exercise, there’s no real reason they can’t.  It would have been nice to see some question raised on how epigenetics gets involved, though. Here, the lack of any suggestion of links is what raises questions — not so much about the story as about what the company is actually doing.

I wrote a post last year on why one might or might not care about ‘business confidence’: basically, it’s not of much real interest in itself, but it may be a leading indicator, a useful predictor of short-term changes in employment or investment.  As I said then “Whether a business confidence survey will be economically useful is an empirical question, to be answered by data.”

In light of the new fall in the business confidence survey, it’s worth noting that this question has been answered by data. The answer is “No”.

David Hood has looked at whether NZ business confidence predicts next-quarter GDP. There’s a weak negative correlation: if business is confident, there’s a slight tendency for the economy to get worse in the next quarter. More dramatically, he finds that business confidence from countries other than NZ is a better predictor of NZ GDP than NZ business confidence is.  If you want to know how the NZ economy is doing, it seems you’d be better off asking Chinese or Swedish or Canadian businesses than Kiwi businesses.

One big component of the problem is that business confidence in NZ has been lower when we have a left-wing government led by a female PM. Since the economy has done better  when we have a left-wing government led by a female PM, we get a negative correlation.  That’s not to say that Labour women necessarily run the economy better; most of the variation isn’t something that the government has much control over; it’s not that Helen Clark was holding off the Global Financial Crisis and electing John Key then let it happen.  Still, when business confidence is affected by that sort of bias it’s not going to be as good an economic indicator, and even when you try to subtract off the bias, there doesn’t seem to be much information in the NZ business confidence index. 

You  might ask why I’m believing some random person on the internet rather than the ANZ survey.  It’s not a matter of reputation — we have the analysis, and StatsNZ has the data. Business confidence surveys can, in some settings, be a useful economic leading indicator.  In New Zealand, they haven’t been.

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 152 matches played, 96 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.

Team Ratings for Round 1

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.

Predictions for Round 1

Here are the predictions for Round 1. 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.

Note that Cheetahs2 refers to the Cheetahs team when there is a Pro14 match. The assumption is that the team playing in the Pro14 is the top team and the Currie Cup team is essentially a second team. Possibly there will be no such clashes this year

Performance So Far

So far there have been 12 matches played, 6 of which were correctly predicted, a success rate of 50%.
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 20

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 20

Here are the predictions for Round 20. 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 4

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.

Note that Cheetahs2 refers to the Cheetahs team when there is a Pro14 match. The assumption is that the team playing in the Pro14 is the top team and the Currie Cup team is essentially a second team. Possibly there will be no such clashes this year

Performance So Far

So far there have been 9 matches played, 6 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Round 4

Here are the predictions for Round 4. 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.

There’s a story at the  Huffington Post, based on a new research paper, saying

Genes account for about 80% of a child’s risk of developing autism, a massive new study finds.

That link is not from the HuffPost story (they don’t link), but via Spectrum News, whose story is similar except they actually use the word “heritability” in a few places.

The abstract of the research paper says

Based on population data from 5 countries, the heritability of ASD was estimated to be approximately 80%, indicating that the variation in ASD occurrence in the population is mostly owing to inherited genetic influences, with no support for contribution from maternal effects.

so this is a case where the claims come from the scientists — but where the claims aren’t as strong before you translate them from Science to English.

If you think about it for a few minutes, it obviously can’t be true in a straightforward sense that 80% of the risk of developing autism is genetic(or, more precisely of being diagnosed with it, since that’s what can be measured).  Autism (diagnosis) is much more common than it used to be. For example, the US Centers for Disease Control report that from 2000 to 2014, “ASD prevalence estimates increased from 6.7 to 16.8 per 1,000 children aged 8 years, an increase of approximately 150%.” Absolutely none of this change is genetic: fourteen years isn’t long enough for population genetic changes. In the US, over that period, something non-genetic that varies with time was responsible for the majority of the autism (diagnosis) risk.  Improvements in diagnosis are probably one contributing factor.

Heritability is an important technical measure that sounds more interesting than it actually is.  It’s related to whether things are genetically determined, but it isn’t the same. For example, in humans, “number of legs” has very low heritability, but the reason nearly everyone has two legs is genetic.

More seriously, suppose that a condition requires both that you have a particular genetic variant and that you experience a particular environmental exposure.  Whether the condition ‘looks’ genetic or environmental will depend on who you compare.  If you compare among people of northern European ancestry living in NZ, melanoma skin cancer looks to be mostly environmental: it’s caused by sunburn.  If you compare among people living in South Africa, melanoma looks substantially genetic: it’s caused by a lack of melanin in the skin, and the genetic contributions to skin colour are moderately well understood.

Team Ratings for Round 19

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 136 matches played, 85 of which were correctly predicted, a success rate of 62.5%.
Here are the predictions for last week’s games.

Predictions for Round 19

Here are the predictions for Round 19. 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.