Posts from April 2017 (34)

From the Herald (from the Daily Mail)

Materials used to fireproof sofas are linked to a 74% rise in thyroid tumours

From the American Cancer Society

The chance of being diagnosed with thyroid cancer has risen in recent years and is the most rapidly increasing cancer in the US tripling in the past three decades. Much of this rise appears to be the result of the increased use of thyroid ultrasound, which can detect small thyroid nodules that might not otherwise have been found in the past.

That is, thyroid cancer looks as if it’s more common at least partly because diagnosis has improved. It could potentially still be true that fire retardants are a problem as well, but the  “killer sofa” people either don’t know about out about the changes in diagnosis or do know but don’t think we need to be told.  Either way, I don’t think it increases their credibility.

• Good piece at Stuff about what a 500-year flood is. The concept isn’t quite as shaky as it sounds — there’s some independent information from comparing different river systems — but it’s inevitably uncertain.

• 23andme is back providing genetic risk information, but in a much more restricted way after FDA review.  A lot of the risk information you can get this way isn’t useful for treatment, but it’s the sort of thing some people like to know.  So, sometimes, do their insurance companies

• The concept of ‘net tax’ — tax paid minus cash benefits and transfers (but not non-cash ones such as Pharmac subsidies) can be a useful concept.  However, I don’t think it’s as useful when ‘tax’ leaves out GST, as in this story at Stuff.  Admittedly, it’s not trivial to calculate how much GST people pay, but I’m sure the Treasury had looked at it.

• Scientists and journalists need to get better at communicating uncertainty, and people need to accept it’s there. (Ed Yong, in the Atlantic)

• Analysis at Pro Publica on minorities paying more for car insurance (in the US) even after adjusting for risk.

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 April 14 2017.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of April 8 – 14 2017 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!

Headline: Research has found that Marmite could help prevent dementia

Research article:  A group of 28 adult volunteers (10 males, mean age 22 years) completed the study after providing written informed consent.

We could just stop there, but it gets better (not better)

The study found that the people getting Marmite had, as hypothesised, less response by their brains to flickering visual stimuli.  The research paper does not mention dementia (or memory, or Alzheimers). At all. It concludes

“This demonstrates that the balance of excitation and inhibition in the brain can be influenced by dietary interventions, suggesting possible clinical benefits in conditions (e.g. epilepsy) where inhibition is abnormal.”

Even the story doesn’t come close to the headline claims, saying just

It could also prompt further research to see if Marmite, and its effect on the brain’s GABA chemical, might provide a treatment for dementia.

And, right at the end of the story, the quote from an independent expert

“there’s no way to say from this study whether eating Marmite does affect your dementia risk.

If it does, and if that’s because of the vitamin B12, it might also have been worth mentioning that there are other foods with as much or more vitamin B12 per serving, such as beef, and lamb, and many types of fish.

• If someone told me a longstanding problem in mathematical statistics had been solved, but then admitted the proof was short, used fairly elementary techniques, was written with Microsoft Word, and was published in the Far East Journal of Theoretical Statistics, I might not be in a hurry to look it up.  These are all genuinely reasonable filters for mathematical papers that are worth putting effort into. But, in this case, they were all false positives. Quanta Magazine has the story.

• From The Conversation,”The seven deadly sins of statistical misinterpretation, and how to avoid them“.

• “Spreadsheets are people, too“

• From Newsroom (who seem to be quite good so far) Interaction of recreational genotyping and health insurance in NZ

• From The Conversation, how website terms of use (and their potential criminal enforcement in the US) affect research into fairness and transparency of algorithms.

• Graphics from Nathan Yau at Flowing Data on when Americans had significant life events, including one on When Straight Americans Lost Their Virginity that was so good the Daily Mail asked to use it, were refused, and used it anyway.

• Good Herald interview on air pollution with NIWA scientist Elizabeth Somervell

In 2015, the Herald had a story from the Daily Telegraph on the alleged risks of margarine:

Saturated fat found in butter, meat or cream is unlikely to kill you, but margarine just might, new research suggests.

Traditionally people have been advised to reduce animal fats, but the biggest ever study has shown they do not increase the risk of stroke, heart disease or diabetes. However, trans fats, found in processed foods such as margarine, raise the risk of death by 34 per cent in less than a decade.

“For years everyone has been advised to cut out fats,” said study lead author Doctor Russell de Souza, an assistant professor in the Department of Clinical Epidemiology and Biostatistics, at McMaster University in Canada.

It’s a bit unclear exactly what “raise the risk of death by 34 per cent in less than a decade” is supposed to mean, but we’ll get to that. The research paper was in the BMJ, and came out on the same day the story did.

Today, in 2017, the Herald had a story from the Daily Telegraph on the alleged risks of margarine:

Saturated fat found in butter, meat or cream is unlikely to kill you, but margarine just might, new research suggests.

Although traditionally dieticians have advised people to cut down on animal fats, the biggest ever study has shown that it does not increase the risk of stroke, heart disease or diabetes.

However trans-fats, found in processed foods like margarine raises the risk of death by 34 per cent.

“For years everyone has been advised to cut out fats,” said study lead author Doctor Russell de Souza, an assistant professor in the Department of Clinical Epidemiology and Biostatistics, at McMaster University in Canada.

It’s a bit unclear exactly what “raise the risk of death by 34 per cent in less than a decade” is supposed to mean, but we’ll get to that. The research paper was in the BMJ, and came out nearly two years before the story did.

Yes, it really seems to be the same ‘new reasearch’: Dr de Souza hasn’t just published another meta-analysis. It even seems to be the same Telegraph story; I couldn’t find a new one.

So, how scared should we be of trans fats in our diets?  Food Standards Australia New Zealand say

Monitoring of TFAs in the Australian and New Zealand food supply has found that Australians obtain on average 0.5 per cent of their daily energy intake from TFAs and New Zealanders on average 0.6 per cent. This is well below the WHO recommendation of no more than 1 per cent.

They also say that the majority of that 0.6% is made by bacteria in the rumens of cows and sheep, not by industrial hydrogenation; the evidence of harm is weaker for these natural trans fats.

Now, back to the 34% statistic. This is based on two studies. One compared the 20% of people with the highest and lowest trans fat intakes and found a rate ratio of 1.24. The other, smaller, one estimated the ratio as 1.71 between the highest and lowest 25%.   These are rate ratios estimated from people in their 60. Since the actual probability of death in any given year would have been about 1% the absolute risk increase is smaller than “34% in less than a decade” sounds — but not at all trivial.  For comparison, the all-cause mortality rate ratio for current smoking is about 3.0, or 200% higher than non-smokers.

More importantly, though, we’re talking about a lot of trans fat in these studies. In the larger study with the less-scary rate ratio, people in the lowest 20% of trans fat intake got an average of 1.6% of their calories from it. That is, the lowest-risk group were eating three times as much trans fat as an average Kiwi today.  In the smaller study, they don’t give actual trans fat information for the groups they are comparing, but the average for the whole study was about 9% of fat in the blood was trans fat: if that even roughly translates to proportions of dietary fat they were also getting more than the typical Kiwi today.

There just isn’t that much trans fat in most margarine any more, less than 1% on average (according to Food Standards Oz/NZ, table 2) . There used to be a lot, but then we found out it’s bad for you.  Those scary numbers are actually good news if they’re true: they’d measure how much better off margarine consumers are today than twenty years ago.

(via Mark Hanna)

In yesterday’s Official StatsChat Bogus Poll, about two-thirds of the respondents got one of the reasonable answers.

Here’s how we could work out most of the answer without looking it up.

First, a hectare is 10,000 square meters, or 2.5 acres (you might need to look that up).

Now, a ‘full section’ for a house is typically less than 1000 square meters (a quarter acre), so you get 10-20 of them per hectare, and maybe 100,000 of them in 7000 ha.  That’s definitely bigger than Eden Park, and it’s pretty clearly bigger than One Tree Hill Domain + Cornwall Park.  In the other direction, 100,000 full sections must be smaller than the Auckland isthmus, and so (look at a map) smaller than Manukau Harbour.

The comparison to Epsom electorate is a little harder, and you might need actual data to decide.

Now, actual data:

The areas are

Eden Park:  originally `about 15 acres’, or 6 ha

One Tree Hill Domain + Cornwall Park: 270 ha

Epsom: 20 sq km, so 2,000 ha

Manukau Harbour: 394 sq km, or 39,400 ha.

Waikato Region: 2.5 million ha.

If you look up the area of  the Auckland isthmus for comparison with Manukau Harbour, you’ll probably get a figure of 638 sq km. That’s the area of the old Auckland City: it includes the Gulf Islands that were part of the city (in particular, Great Barrier and Waiheke make up more than half of it). It’s surprisingly hard to find the area of the isthmus itself on the internet.

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 49 matches played, 39 of which were correctly predicted, a success rate of 79.6%.
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.

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 40 matches played, 22 of which were correctly predicted, a success rate of 55%.
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.