Posts filed under General (3152)

• “What CPE—and the field—needs now are analysts. Lots and lots of analysts. And we, at least, are hiring DataNerds who want to be JusticeNerds™. With departments now coming in by the state-load, we are inundated with confidential data that needs to be interrogated so that we can answer some of the most fundamental questions in policing” from Phil Goff (no, not that one) at the Center for Policing Equity, via mathbabe.org

• If someone claims your female developers are promoted less because they’re treated worse at code review, and you say “no, they’re treated worse because they’re more junior”, you’ve made the basic causal-inference error of conditioning on an intermediate consequence of your input variable.  Felix Salmon on Facebook’s example

• “For too long social welfare has muddled along with bipartisan policies like shouting at the jobless or not helping people with mental health issues, without really checking if those methods work.” This, from, Lyndon Hood, isn’t going where you might expect.  It’s unfair, but not completely unfair.

• Another reason ‘breakthrough’ science stories may be misleading: there was a research paper claiming fish preferentially eat microplastic pollution and are serious harmed by it. It has been retracted. There are allegations of deliberate fraud; the data were certainly not made available as the journal’s policy demanded.  If you remember a story on this, go back and see if the same media outlet covers the retraction.

• I’ve written a few times about the bogus claim that the typical Kiwi pays no “net tax”.  In the other direction, there were stories about  “Tax Freedom Day” this week, on the basis of 34.8% of income going in tax. Yeah, nah.

• Derek Lowe writes about a new analysis looking at solanezumab, Eli Lilly’s failed treatment for Alzheimer’s. The analysis claims that if the drug had been approved based on the early, weak signals of benefit, the cost to the US government would have been about ten billion dollars over the past four years. That would pay for a lot of trials, or for a lot of other improvements to dementia care.

• There’s publication bias in research on stock-market patterns. Because of course there is.

• Somewhat depressingly, someone has looked what people write when they apply for loans at peer-to-peer lending site Prosper (like Harmoney here in NZ). The phrases most indicative of the loan defaulting: “God, promise, will pay, thank you, hospital.”   (via Matt Levine, who isn’t surprised)

This was almost too good to check

Know there’s a lot of news out there about France right now, but I just found out a pie graph is called a Camembert.

— Lauren Collins (@laurenzcollins) May 8, 2017

And this was too good to ask if it’s a joke:

(it is)

Team Ratings for Round 12

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 87 matches played, 67 of which were correctly predicted, a success rate of 77%.
Here are the predictions for last week’s games.

Predictions for Round 12

Here are the predictions for Round 12. 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 11

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 79 matches played, 60 of which were correctly predicted, a success rate of 75.9%.
Here are the predictions for last week’s games.

Predictions for Round 11

Here are the predictions for Round 11. 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 10

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 72 matches played, 40 of which were correctly predicted, a success rate of 55.6%.
Here are the predictions for last week’s games.

Predictions for Round 10

Here are the predictions for Round 10. 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 Guardian about whether there has been a ‘pause’ and an ‘acceleration’ in global warming.  The underlying research paper actually puts the question more clearly

While it is clear and undisputed that the global temperature data show short periods of greater and smaller warming trends or even short periods of cooling, the key question is: is this just due to the ever-present noise, i.e. short-term variability in temperature? Or does it signify a change in behavior, e.g. in the underlying warming trend?

Models for climate change predict that annual mean surface temperature should be going up fairly smoothly, so that the trend over a decade or so looks like a straight line. A deviation from this trend might indicate important factors have been left out of the model, or might indicate that the background processes are changing (eg as ice sheets retreat).  If you look at the recent past, compared to a straight-line trend, the observed data dipped below the straight line for a few years and have now caught up.  This raises the question of whether either of these indicated an important change in the underlying processes or a new inadequacy of the models.

To start with, let’s establish that we’re not talking about measurement error here.  The variability of annual mean temperatures around the straight-line trend isn’t like the variability of opinion poll results around a trend. The observed data are the truth.  The world really did warm less for a couple of years; it really has warmed more since then.  The straight line trend omits many factors that we know are relevant: events such as volcanic eruptions that affect the incoming sunlight, and events such as El Niño that affect the balance between air and ocean warming.

The question is whether the straight line trend is changing (fast enough to worry about).  You might reasonably object that the annual mean temperatures are far too crude to make that sort of decision; that you need much more details and more sophisticated modelling. As it turns out, you’d be right. However, the crude appearance of a slowdown and speedup in the annual means has been the fuel for a lot of discussion, so it’s worth evaluating.

What the research paper did was to model the deviations from the straight line trend as a simple random process, ignoring any year-to-year correlation.  The researchers could then evaluate mathematically how likely we would be to see an apparent pause or acceleration in warming with that amount of random variation, if in fact the trend was a perfect straight line. The deviations we have seen in the recent past are no larger than you’d expect just from the variation around a constant trend.

To be clear, this doesn’t mean there have been no changes in the trend.  In fact, we know that El Niño does cause systematic changes.  What it means is that the annual mean temperatures alone aren’t enough information to tell us about changes over a period as short as a few years. You shouldn’t change your beliefs (in any direction) over data like that. If the ‘hiatus’ had gone on for a decade, it would have meant something. If the acceleration goes on for a decade, it will mean something. But two or three years isn’t long enough to say anything.  It’s like looking at a month of data on road deaths: you can’t — or at least shouldn’t  — say much.

On Wednesday, the NZ Herald website featured a story and graphics by Harkanwal Singh and Lincoln Tan on immigration. This story was based on permanent and long-term migration data from Statistics New Zealand. The graphics allowed readers to explore the data for themselves. The data source was accurately described and was well targeted to the current political discussion about changing immigration policies.

The specific data set and visualisation used are not the only possible ones, and reasoned criticism of the data and analyses is entirely legitimate. StatsChat encourages that sort of thing. We have done it ourselves, and we have published links when other people do it.

Winston Peters, however, claimed that the Herald story was “fake news” and attributed the conclusions to the reporters being Asian immigrants themselves. The first claim is factually incorrect; the second (in the absence of convincing evidence) is outrageous.

James Curran (Professor of Statistics)
Thomas Lumley (Professor of Statistics)
Chris Triggs (Professor of Statistics)

Team Ratings for Round 9

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 64 matches played, 36 of which were correctly predicted, a success rate of 56.2%.
Here are the predictions for last week’s games.

Predictions for Round 9

Here are the predictions for Round 9. 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 10

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 71 matches played, 55 of which were correctly predicted, a success rate of 77.5%.
Here are the predictions for last week’s games.

Predictions for Round 10

Here are the predictions for Round 10. 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.

• The Herald (from the Daily Mail) recommends drinking beetroot juice, based on a study of brain waves: “This finding could help people who are at-risk of brain deterioration to remain functionally independent, such as those with a family history of dementia“.  The NHS Choices blog commented on a similar study by the same research group in 2010; their comments still apply.

• Testimonials and motivational speakers tell you “I did this and look how it turned out”.  As XKCD illustrates, results may not be typical 

• “Data made available for reanalysis, a journal that promptly responded to the outcomes of that reanalysis, and a finding that could save lives.” (from Stat). Another moral to the story: don’t edit data by copy-and-paste.

• “The company says it has studies that back up its claims, but refused to release them on the grounds that they are commercial-in-confidence.” It appears that Johnson & Johnson would rather pull their ad than let people look at the evidence. (from The Age)

• “it’s not acceptable if you’ve got the information readily available to leave it to the last minute for release, that’s not what the Act says you can do”  The Chief Ombudsman interviewed by Newsroom  about the Official Information Act.

And finally

I ended a recent #SciComm talk with this slide of questions scientists should answer even if they’re not asked: pic.twitter.com/N88LuuSBoM

— Rachel Feltman (@RachelFeltman) April 11, 2017

So, the Herald (from the Daily Mail) has a headline Why women should eat a punnet of strawberries a day. That seems a little extreme, especially as punnets of strawberries are fairly seasonal.

The story leads off with

Eating just 15 strawberries a day protected mice from aggressive breast cancer in a new medical study.

So, first of all, mice, not women.  Also, when you go to the open-access research paper, it didn’t exactly ‘protect’ the mice.  The mice had cells from a breast cancer cell culture implanted under their skins, and the study looked at the change in size of those implanted tumours, not at spread within the mouse or health of the mouse or anything like that.  It’s a useful approach to learning about cancer cell biology, but not all that close to preventing or treating human cancers.

More surprisingly, though, “15 strawberries a day” seems quite a lot for a mouse — several times its body weight. The story changes a bit later:

In total, the strawberries made up 15 percent of the mice’s diet. That is just shy of the recommended daily amount of fruit we should eat each day, and would be equivalent to a punnet of strawberries, reported the Daily Mail.

A figure of 15% seems more plausible than 15 strawberries, though it’s still not quite true, since actually the mice were given concentrated strawberry extract in their food rather than strawberries.  Using the standard (lowish) estimate of 2000 kcal/day, 15% of calories would  be 300 kcal/day  which would take nearly a kilogram of strawberries.

Previous studies have already shown that eating between 10 and 15 strawberries a day can make arteries healthier by reducing blood cholesterol levels.

There isn’t a reference, but the same researcher has studied strawberries and cholesterol (this time even in humans). The ‘between 10 and 15 strawberries a day’ was actually 500g per day.

[via Sam Warburton]