March 5, 2012

Think of a number, then double it

The Herald

More than 25,000 animals including fish have died during research and teaching at the University of Otago since 2009, and the figures are expected to increase significantly when statistics are collated for 2011.

No, really?  Going from a two-year total to a three-year total will result in an increase?

We collect multiple years of data for two main reasons: to compute averages (reducing statistical noise) and to compute differences (to learn about trends). Computing totals across multiple years is rarely helpful.

The Otago Daily Times does a better job: it uses the multiple years of data to give trends

Animal use by different groups in New Zealand has dropped by 29% during a three-year period from a record high of 341,520 recorded in 2008.


The number of animals being used for research purposes by universities in 2010 has dropped 43% from a high of 123,739 in 2008.


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 »


  • avatar

    Actually they were both ODT stories, but the NZ Herald only picked up one. The ODT ran the shock horror one plus the context piece.

    6 years ago

  • avatar

    This morning Radio NZ National highlighted two news from the ODT frontpage: University animal death toll tops 25,000 and Students disciplined by antisocial behaviour. I couldn’t stop making the (inexistent AFAIK) connection.

    The ODT also makes a funny distinction between animals and fish, and there is no mention to invertebrates (many of which probably do not require approval from the ethics committee).

    6 years ago

    • avatar
      Thomas Lumley

      Most invertebrates don’t require approval, though cephalopods do, as do crabs and lobsters and their ilk.

      I’m a bit surprised by the small numbers for fish in the full report — I thought there would be more use of zebrafish in lab research.

      6 years ago

  • avatar
    Murray Jorgensen

    For more context still these numbers might be compared with the numbers killed annually at NZ slaughterhouses.

    6 years ago