Posts from April 2015 (35)

So, I was on a plane from Sydney yesterday that was old enough they told us to switch off our books half an hour before landing. As a result, I actually looked at the Auckland information on the flight map channel (photo taken after we were allowed technology, naturally):

It’s interesting to see where these numbers come from, given all the different ways these things can be defined. Two of these numbers are inconsistent with each other and somewhat obsolete, and the third isn’t even wrong.

According to the Google, the population number 1,377,200 is the June 2011 estimate of the urban population of the Auckland metropolitan area.  Ok, that’s a bit old but so was the plane. Slightly more strange is that StatsNZ thinks the urban Auckland population at 30 June 2011 was 1,351,200, but that’s probably a matter of projections being made in advance and then adjusted as more information comes in. The current (June 2014) estimate is 1,413,500.

So if the population is urban Auckland, what’s the area? With a bit of searching, you can find it’s the area of the old Auckland City, the central Auckland isthmus plus various islands. Auckland City had a population of 450,000 when it was absorbed into the Supercity in 2010. The population and area numbers are for very different entities, and the population number, although old, dates from after the area number became completely obsolete.

The area that goes with the 1,377,200 number is 1,102.9km², the size of the Statistical Urban Area. You could reasonably want the urbanised area (483km²) or the Metropolitan Urban Limits (560km²) as better summaries of the size of Auckland, but they don’t match the quoted population.

That leaves elevation. The picture next to the statistics shows that 78m is not a completely satisfactory characterisation of the elevation of Auckland. The blue stuff with boats floating on it is at sea level (up to tidal variation). Here’s a map (from FloodMap.net) of Auckland elevation; the change from pink to red is at 75m.

Overall, population and area, which could have multiple satisfactory definitions, are defined incompatibly with each other.  Elevation doesn’t really have a satisfactory definition, but isn’t 78m.

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 10 2015.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of April 4 – 10 2015 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.

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If you’d like to comment on or debate any of this week’s Stat of the Week nominations, please do so below!

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.

Performance So Far

So far there have been 32 matches played, 19 of which were correctly predicted, a success rate of 59.4%.

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 8

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 47 matches played, 31 of which were correctly predicted, a success rate of 66%.

Here are the predictions for last week’s games.

Predictions for Round 8

Here are the predictions for Round 8. 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.