Posts filed under Silly (63)

January 2, 2015

Using the right denominator

We go on and on about denominators on StatsChat: the right way to report things that happen to people is usually a rate per capita rather than a total, otherwise you end up saying that Auckland has the highest number of whatever it is in New Zealand.  You do have to use the right denominator, though.

The Vatican City has the world’s highest crime rate.

That’s because the permanent population is less than 500, but the daily tourist population is about 100 times larger. The right denominator would be the tourist population.

In most countries this isn’t really an issue. For example,  in New Zealand,which has a lot of tourism, short-term visitors are only about 5% of the population. Even in the Cook Islands, residents outnumber tourists.

 

Maybe not a representative sample

The Dominion Post asked motorists why they thought the road toll had climbed, and what should be done about it.

roadtoll

Interestingly, three of the five(middle-aged, white, male ,Wellington area) motorists attributed it to random variation. That’s actually possible: the evidence for a real change in risk nationally is pretty modest (and the Wellington region toll is down on last year).

(via @anderschri5 on Twitter)

Meaningless bignums

From the science journal Nature, who should know better than to quote big-sounding numbers without context.

B6R7QaNCIAI2Qsx

That’s roughly the same number of person-hours as the world spent watching the China Central Television news program Xīnwén Liánbō: estimated at 135 million people for half an hour a day.  Or about 1/3 as much time as spent watching YouTube.

 

December 29, 2014

Set to a possibly recognisable tune

The Risk Song: One hundred and eight hazards in 80 seconds

(via David Spiegelhalter)

December 27, 2014

The Lesser Spotted Hutt Man Drought

From the Christmas Eve edition of the Upper Hutt Leader, which you can read online:

Ladies, be warned — Upper Hutt is in  the grip of a man drought

Here’s the graph to prove it (via Richard Law, on Twitter)

 upperhuttleader

 

As the graph clearly indicates, women outnumber men hugely in the 25-35 age range, and (of course) at the oldest ages. The problem is, the y-axis starts at 45%. For lines or points that’s fine, but for bar charts it isn’t — because the bars connect the points to the x-axis.

This is Stats New Zealand’s version of the graph, in standard ‘population pyramid’ form. It’s much less dramatic.

dbimages

We could try a barchart with axis at zero

huttzero

It’s still much less dramatic — and you can see why the paper chopped the ages off at 75, since using the full range available in the data wouldn’t have fit on their axes.  The y-axis wasn’t just trimmed to fit the data; it was trimmed beyond the data.

You could make a case that ‘zero’ in this example is actual 50%: we (well, not we, but journalists who have to fill space) care about the deficiency or surplus of members of the appropriate sex.

hutt50

Or, you could look at deficiency or surplus of individuals, rather than percentages

huttdiff

Using individuals makes the younger age groups look more important, which helps the story, but on the other hand shows that the scale of this natural disaster isn’t all that devastating.

That’s basically what the expert quoted in the story says. Prof Garth Fletcher, from VUW, says

“People in Upper Hutt or Lower Hutt, they go to parties, they go to bars, they go to places in the wider Wellington area.”

It was only when you started having a gap between men and women of more than 5 or 10 percent that there would be real world implications, he said.

 

[Update: My data and graphs are for Upper Hutt (city). That’s about 2/3 of the Rimutaka electorate, which is where the paper’s data are for]

December 23, 2014

What’s the chance of that?

The best law-of-large-numbers scene in modern cinema.

“A spectacular vindication of the principle that each individual coin, spun individually, is as likely to come down heads as tails, and therefore should cause no surprise each individual time it does”

 

December 22, 2014

Solstice, Christmas, and the Phantom Time Hypothesis

Today (in NZ) is the summer solstice, the time when the sun is the highest in the sky, and the longest day. In the northern hemisphere it’s the winter solstice, the darkest day of winter.

The date of Christmas, as every school child knows, wasn’t even in theory chosen as the anniversary of a particular night when shepherds were abiding in the fields. Views differ on whether it was chosen to match the Roman solstice celebration on December 25th, or nine months after the equinox on March 25th. In either case, though, we seem to be off by a few days. Today is the solstice and nine months after the equinox, but Christmas isn’t until Thursday. Why could that be?

One possibility, advanced by German historian Heribert Illig, is that the date isn’t really 2014 this year. It’s really only 1717, so we haven’t had enough missing leap years since the year 1 CE and the Gregorian calendar is off by a few days. That is, according to Illig, the period from 614 CE to 911 CE didn’t happen. The evidence adduced for this gap, in addition to the date of Christmas, is a shortage of buildings in Constantinople (now Istanbul) in that period, and a gap in Christian theological development.

Back in consensus reality, the Phantom Time Hypothesis provides a nice illustration of how data in different fields interlocks like a crossword puzzle.  For example, the times of historical eclipses and sightings of Halley’s Comet match the standard calendar, and don’t match if you assume there are three missing centuries, and the same is true of tree ring counts, and the last big eruption at Lake Taupo. And while the history of Rome and Constantinople is arguably tidier in some ways, there’s a hole blown in the middle of  the Tang Dynasty, including important events such as the Battle of Talas.

So, is there a better explanation of why today isn’t Christmas? In fact, yes. When the Gregorian calendar was devised, it didn’t try to go all the way back to 1CE, which people already realised was a slightly iffy date at best. It was designed to match the Julian calendar in 325CE: the date of the Council of Nicea, when the formula for the date of Easter was agreed on (and where Nicholas of Myra, aka Santa Claus, was thrown in jail for slapping Arius during a debate)

StatsChat wishes you a happy summer or winter solstice.  Try to refrain from slapping anyone, whatever the provocation.

December 18, 2014

It’s beginning to look a lot like Christmas

In particular, we have the Christmas issue of the BMJ,  which is devoted to methodologically sound papers about silly things (examples including last year’s on virgin birth in the National Longitudinal Study of Youth, and the classic meta-analysis of randomised trials of parachute use)

University of Auckland researchers have a paper this year looking at the survival rate of magazines in doctors’ waiting rooms

We defined a gossipy magazine as one that had five or more photographs of celebrities on the front cover and a most gossipy magazine as one that had up to 10 such images. The Economist and Time magazine were deemed to be non-gossipy. The rest of the magazines did not meet the gossipy threshold as they specialised in, for example, health, the outdoors, the home, and fashion. Practice staff placed 87 magazines in three piles in the waiting room and removed non-study magazines. To blind potential human vectors to the study, BA marked a unique number on the back cover of each magazine. Twice a week the principal investigator arrived at work 30 minutes early to record missing magazines.

And what did they find?

F1.large

 

 

December 14, 2014

Statistics about the media: Lorde edition

From @andrewbprice on Twitter: number of articles in the NZ Herald each day about the musician Lorde

lorde

The scampi industry, which brings in similar export earnings (via Matt Nippert), doesn’t get anything like the coverage (and fair enough).

More surprisingly, Lorde seems to get more coverage than the mother of our next head of state but two.  It may seem that the royal couple is always in the paper, but actually whole weeks can sometimes go past without a Will & Kate story.

November 16, 2014

John Oliver on the lottery

When statisticians get quoted on the lottery it’s pretty boring, even if we can stop ourselves mentioning the Optional Stopping Theorem.

This week, though, John Oliver took on the US state lotteries: “..,more than Americans spent on movie tickets, music, porn, the NFL, Major League Baseball, and video games combined. “

(you might also look at David Fisher’s Herald stories on the lottery)