Exploring Data on a Rare Threatened Bird – the Rock Wren

Ian Westbrooke

A possible decrease in number of Rock Wren in the Fiordland area of New Zealand between 1985 and 2005 is investigated.

Numbers are recorded in 12 grids of 25 hectares at the two points in time.



The file Wren bird data.xls contains the data analysed.

  • The file Task 1.pdf describes a procedure using the spreadsheet Bootstrapping Wren data.xls for constructing a bootstrap confidence interval for the mean of the changes in the number of Wren observed between 1985 and 2005. We shall not use this procedure here.)
  • Instead an alternative bootstrap program in a file called bootstrapper.xls should be used either to carry out the procedure for the samples of counts from 1985 and 2005 or for the single sample of differences. Comment on the advantage of using the single sample of differences.
  • A second task explores the data graphically. This is described in the video.
  • A third task calculates the normal confidence interval for the changes in Wren counts. This is also described in the video using Excel. The Bootstrap confidence intervals can then be compared.

If you have access to GenStat, you can go through the lesson Wren-GenStat.pdf

Video content recorded and edited by Robert van der Vyver[1] and John Harraway[2].
Web site developed and maintained by Greg Trounson[2] and John Harraway
Contact us

1: Higher Education Development Unit, University of Otago
2: Department of Mathematics and Statistics, University of Otago