It is always difficult to compare accidents rates for 'rare' events due to the wide 95% confidence intervals. http://www.evanmiller.org/ab-testing/poisson-means.html
As mentioned by others, there often needs to be an order of magnitude difference (i.e. a 10 tenfold increase or decrease of an accident rate) to demonstrate statistical significance at the 95% level (this also means that there is a 5% chance of accepting a chance variation as being significant). It is not lies and damned statistics, but a 5% chance that the result is in error (using commonly accepted practice). See: https://en.wikipedia.org/wiki/Poisson_distribution Comments from statisticians welcome. Mark Newton's comments about threat and error management are very useful! _______________________________________________ Aus-soaring mailing list [email protected] http://lists.base64.com.au/listinfo/aus-soaring
