Stats Chat

I’ve written before about the problem of unpublished science in the news: the news story won’t (can’t) give much detail, and there’s no way to find it out.  Stuff has gone one step further:

Recent animal studies show sleep’s cleansing process in action. But now scientists at Oregon Health & Science University are preparing to conduct a study on humans that would further explain deep sleep’s effect on human brains.

The ‘animal studies’ claim comes without any source. Fortunately the Google comes to the rescue and suggests it’s the research in this story from 2013. Interestingly, a couple of subsequent mouse studies have also found brain problems from interrupted sleep — but since each of the three studies found a different problem, with no overlap, this isn’t as supportive as it sounds.

It would matter less if it weren’t for the first sentence of the story

Forget about needing beauty sleep. It’s your brain that may suffer the most from a lack of deep shut eye.

There’s a definite suggestion that this is a risk factor you can do something about, especially as this is in the “Well & Good” section of the Stuff site.

Even if the Oregon research had been carried out and published, it might well not justify that sort of implication. Research that they’re still preparing to do certainly doesn’t.

[Update: It’s getting to be a trend: the Herald also has a story about research that hasn’t happened yet, on addiction.]

The Icelandic Ethical Humanist Association commissioned a survey on religion. For people who don’t want to read the survey report (in PDF, in Icelandic), there’s a story at Iceland Magazine. The main point is in the headline: 0.0% of Icelanders 25 years or younger believe God created the world, new poll reveals.

That’s a pretty strong claim, so what did the survey actually do? Well, here you do need to read the survey report (or at least feed snippets of it to Google Translate). Of the people they sampled, 109 were in the lowest age category, which is ‘younger than 25’.  None of the 109  reported believing “God created the world” vs “The world was created in the Big Bang”.

Now, that’s not a completely clean pair of alternatives, since a fair number of people — the Pope, for example — say they believe both, but it’s still informative to some extent. So what can we say about sampling uncertainty?

A handy trick for situations like this one is the ‘rule of 3’.  If you ask N people and none of them is a creationist, a 95% confidence upper bound for the population proportion is 3/N. So, “fewer than 3% of Icelanders under 25 believe God created the world”

The Dominion Post has what I’m told is a front page story about school costs, with some numbers:

For children starting state school this year, the total cost, including fees, extracurricular activities, other necessities, transport and computers, by the time they finish year 13 in 2028 is estimated at $35,064 by education-focused savings trust Australian Scholarship Group.

That increases to $95,918 for a child at a state-integrated school, and $279,807 for private school.

Given that the figures involve extrapolation of both real cost increases and inflation thirteen years into the future, I’m not convinced that a whole-education total is all that useful. I would have thought estimates for a single year would be more easily interpreted.  However, that’s not the main issue.

ASG do this routinely. They don’t have the 2016 numbers on their website yet, but they do have last year’s version. Important things to note about the numbers, from that link:

ASG conducted an online education costs survey among its members during October 2013. The surveys covered primary and secondary school. In all, ASG received more than 1000 survey responses.

So, it’s a non-random, unweighted survey, probably with a low response rate, among people signed up for an education-savings programme. You’d expect it to overestimate, but it’s not clear how much. Also

Figures have been rounded and represent the upper ranges that parents can reasonably expect to pay

‘Rounded’ is good, even though they don’t actually show much sign of having been rounded. ‘Represent the upper ranges’ is a bit more worrying when there’s no indication of how this was done — and when the Dom Post didn’t include this caveat in their story.

Every summer, the Department of Statistics offers scholarships to a number of students so they can work with staff on real-world projects. Hubert, right, is working on ways to graphically represent community conservation efforts with Associate Professor Rachel Fewster. Hubert explains:

“Conservation efforts are needed to protect the natural flora and fauna of our beautiful country. This exciting project involves preparing and analysing data collected from volunteers involved in conservation efforts against pests such as rats.

“The data is analysed and uploaded to a website called CatchIT, which is an interactive website that allows the bait and trap information to be presented in graphic form to volunteers, which provides feedback on their pest-control efforts. The data comes to life on the screen, and this engages current and future volunteers in tracking the success of their pest-control projects.

“I am in the final year of my Bachelor of Science majoring in Statistics and Biological Science, having previously finished a Bachelor of Pharmacy (Hons). Statistics has a wide applicability to a wide range of disciplines, and appeals to me because I am passionate about the simple process of getting the most from raw data. It is a very rewarding process knowing that you can make the data more appealing and important to the end user.

“This summer, besides doing this studentship, I’ll be enjoying the sunshine, and relaxing on the beach with family and friends.”

Every summer, the Department of Statistics offers scholarships to a number of students so they can work with staff on real-world projects. Alexander, right, is exploring New Zealand mortality data with Senior Research Fellow Andrew Sporle. Alexander explains:

“The goal is to construct an online data visualiser that will enable the user to analyse and visualise complex population data by simply pointing and clicking from a selection of menus.  This involves collating health and population data and creating software that automatically does the complex statistical calculations based on the user’s selections, but in a way that ensures the confidentiality of the information. This project is part of a larger project on preventable Māori mortality funded by the Health Research Council.

“Our health infrastructure in New Zealand has some of the best and most comprehensive datasets available in the world and, it will be very useful to streamline the analysis process so that users without advanced statistical training can see and understand what is going on. In the longer term, this approach could also be applied to other health and social data, making data more accessible and useful.

“I have recently finished my undergraduate degree in science, majoring in statistics and computer science. I am looking to progress in medical statistics for my honours degree.

“Statistics appeals to me because I am passionate about figuring out ways to develop and enhance understanding between cause and effect, and use that to make improvements – whether small or large, intricate or structural – to whatever situation I find myself in.

“Over summer, I hope to fit in some travel, try to get to the beach, and go tramping; Great Barrier Island will be the first port of call.”

From David Spiegelhalter, at the Understanding Uncertainty blog

Last week, the Chief Medical Officer announced new guidelines for alcohol consumption. The summary says:

‘The proposed guidelines and the expert group report that underpins them, have been developed on the basis of the following principles: People have a right to accurate information and clear advice about alcohol and its health risks.

‘There is a responsibility on government to ensure this information is provided for citizens in an open way, so they can make informed choices.’

This admirable aim of treating the public as adults capable of making up their own minds seems in stark contrast with the authoritarian tone of publicity from the Department of Health, which baldly says: ‘Men should not drink more than 14 units of alcohol each week, the same as women’.

Read the rest

Following up on the recording-breaking Powerball jackpoint in the US, there’s a story on Time.com headlined “The One Time It’s Mathematically Advantageous to Play Powerball.”  They’re still wrong, but they have taken many more of the relevant factors into account than usual, and it’s definitely worth reading.

On top of the microscopic chance of getting the winning numbers, they also look at the likelihood that you will have to share the jackpoint, the benefit of the minor prizes,  the US federal tax payable on the winnings, and the fact that the advertised payout is actually inflated by about 60% — it’s the total future payment for a 30-year annuity you can buy with the prize, not the value of the prize itself.

They come to the conclusion that a jackpot worth more than about $2.2 billion is worth buying tickets for, in the sense that it has positive expected cash return.  The one thing they don’t take into account is the non-linear utility of money. Two billion dollars isn’t actually worth two billion times as much as one dollar, unless you’re the US government or something.  If this sounds strange, all that it’s saying is that each extra dollar is worth more to you than it is to a billionaire.

The diminishing value of extra money means that playing the lottery basically can’t be worthwhile if you evaluate it in terms of winning. The only way playing the lottery can make sense is if you get enough enjoyment from thinking about winning to be worth the upfront cost.

Every summer, the Department of Statistics offers scholarships to a number of students so they can work with staff on real-world projects. Christopher, right, is working with Associate Professor David Scott on All Blacks-related data. Christopher explains:

“My project is aimed at predicting the career lengths of current and future All Blacks based on data from all of the past All Blacks. This project will be useful as it will aid the planning within the All Blacks camp.

“This coming year, I will be studying a research-based MSc in Statistics. My thesis is in the area of quantitative fisheries science and will involve translating ADMB code into STAN code.

“Statistics appeals to me because of its diversity. For example, one day you could be analysing fisheries data, and the next, data relating to the All Blacks.

“In my spare time I enjoying walks along the beach, sailing and cycling around the waterfront with my wife.”

From the Herald, using data from Seek.co.nz: Pay shock: Wellington, not Auckland, is the New Zealand city with the highest advertised salaries.

According to the New Zealand Income Survey, the Wellington region has had the highest median weekly earnings for people in paid employment every year since at least 2007., so the shock should have had time to sink in by now. Looking at NZ.Stat, that’s also true for average weekly earnings.

However, when looking at actual earnings rather than advertisements at one site, Wellington’s percentage lead was only about half as big. And, of course, the actual dollar amounts are lower.

Every summer, the Department of Statistics offers scholarships to a number of students so they can work with staff on real-world projects. Katie, right, is working on the New Zealand Socio-Economic Index with Dr Barry Milne of COMPASS (Centre of Methods and Policy Application in the Social Sciences) and Professor Alan Lee from the Department of Statistics. Katie explains:

“The New Zealand Socio-Economic Index (NZSEI) assigns occupations a score that enables us to measure the socio-economic status of people in that occupation. It’s calculated using the average age, income and education level of people with each job. For example, doctors would have a very high socio-economic index, because they’re typically high-earning and well-educated people.

“The NZSEI has been created from Census data since the 90s, but has not yet been updated for the most recent Census in 2013. In this project, my job is to update the NZSEI using path analysis, and check that this updated version is appropriate for all people in New Zealand. A couple of examples include assessing that the index is valid for all ethnicities, and valid for workers in both urban and rural regions.

“The index is important to measure any changes to New Zealand over time, as it is updated with each Census. As well as this, the NZSEI uses a similar methodology to international scales, so international comparisons are possible.

“I am currently in my third year of studying Mathematics and Statistics at the University of Sheffield in England, and I’m halfway through my year here in Auckland as an exchange student. I’ve always been interested in Statistics and studying it at university level has shown me how applicable it is in a variety of fields, from finance to biology.

“Over the summer, I’m looking forward to exploring New Zealand more.”