Random vs systematic variation
When looking at variation in any sort of proportion, the first step is to work out how much is random variation and how much is systematic and so can perhaps be interpreted or improved. This is the same principle that makes the ‘margin of error’ important in opinion polls.
In Stuff’s release of the National Standards data there is a ‘Download the data’ link. They have censored a few measurements for privacy reasons, which makes sense. They have also left out the sample sizes: how many students is each number based on? For the overall school standards it would be tedious but possible to put this back in by hand using their ‘School Report’ search function, but not for the comparisons broken down by gender and ethnicity.
As an illustration of why this matters, there are multiple schools where 100% of the Maori students are reading at or above the National Standard, and there don’t seem to be any where 100% of all the students are reading at or above standard. What conclusion would you draw from this about Maori vs Pakeha education in NZ?
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 »
As well, the ‘data’ is presented to 2dp.
I think it would be lucky to be ‘accurate’ to +-5 if that.
How come their expert in stats allowed them to get away with that.
12 years ago