Sometimes a pie chart is enough
From Kirsty Johnson, in the Herald, ethnicity in the highest and lowest decile schools in Auckland.
Statisticians don’t like pie charts because they are inefficient; they communicate numerical information less effectively than other forms, and don’t show subtle differences well. Sometimes the differences are sufficiently unsubtle that a pie chart works.
It’s still usually not ideal to show just the two extreme ends of a spectrum, just as it’s usually a bad idea to show just two points in a time series. Here’s the full spectrum, with data from EducationCounts
[The Herald has shown the detailed school ethnicity data before in other contexts, eg the decile drift story and graphics from Nicholas Jones and Harkanwal Singh last year]
I’ve used counts rather than percentages to emphasise the variation in student numbers between deciles. The pattern of Māori and Pacific representation is clearly different in this graph: the numbers of Pacific students fall off dramatically as you move up the ranking, but the numbers of Māori students stabilise. There are almost half as many Māori students in decile 10 as in decile 1, but only a tenth as many Pacific students.
If you’re interested in school diversity, the percentages are the right format, but if you’re interested in social stratification, you probably want to know how students of different ethnicities are distributed across deciles, so the absolute numbers are relevant.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »
MAGS, decile 8, has seven sports academies, a climbing wall, a computer centre, a library, a high quality astronomical telescope, two gymnasiums with a fitness centre, squash courts, school farm and astrograss tennis/netball courts, a 25-metre competition pool, wave pool, two spa pools, a steam room and sauna.
They are also getting $6,000,000 spent on new classrooms, a modernised health centre, room for a career’s department and a renovated students centre.
A low decile school would have to be pretty magical to beat that as the preferred option.
9 years ago
http://www.radionz.co.nz/news/national/281871/more-students-at-poorest-schools
I was a bit surprised to see more students in Dec 10 schools than others (given the meaning of Decile) – seems the reason is the numbers were just about to be revised
9 years ago
It’s also for two other reasons: the deciles are deciles of schools, not students, and the data are only from Auckland, which is oversupplied with decile 10 schools.
9 years ago