Is family violence getting worse?
Stuff thinks so, but actually it’s hard to say. The statistics have recently been revised (as the paper complained about in April).
The paper, and the Labor spokewoman, focus on the numbers of deaths in 2008 and 2011: 18 and 27 respectively.
The difference between 18 and 27 isn’t all that statistically significant: a difference that big would happen by chance about 10% of the time even assuming all the deaths are separate cases. It’s pretty unlikely that the 50% difference reflects a 50% increase in domestic violence, but it might be a sign that there has been some increase. Or not.
The Minister doesn’t do any better: she quotes a different version of the numbers, women killed by their partners (6 in 2008, 14 in 2009, 9 in 2011), as if this was some sort of refutation, and points to targets that just say the government hopes things will improve in the future.
There’s no way that figures for deaths, which are a few tenths hundredths of a percent of all cases investigated by the police, are going to answer either the political fingerpointing question or the real question of how much domestic violence there is, and whether it’s getting better or worse. It’s obvious why the politicians want to pretend that their favorite numbers are the answer, but there’s no need for journalists to go along with it.
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 »