> I've not seen them described that way in the road safety literature that I'm > familiar with. How would that work? If the number of accidents is on the Y > axis, what variable would the X axis have? If we go with road accidents (my > field of expertise) it can't be age/driving experience, because the accident > stats in NO way form a poisson distribution when age/experience is your > X-axis variable. (Actually, road prangs by age/experience gives you more of a > U-shaped curve.) Also, rate of accidents (be they road prangs or glider > prangs) aren't constant over time (as required for a poisson distribution to > be your distribution of choice) - they vary by time of day, for fairly obvious reasons, as well as other things (day of the week, long weekends, etc etc).
> You appear to be approaching the issue from a rather different statistical > approach to the ones I'm familiar with. Could you spell out your > approach/methods in more detail? It's always interesting to hear how folk in > other fields approach problems I'm familiar with. :-) I am approaching it as counting events occurring over a duration of time (analogous to say counting disintegrations per second for radioactive decay). Y axis would be the accident rate with any metric that you care to choose (i.e. accidents per 1,000 hours flown, accidents per 100km travelled, accidents per 1,000 flights etc.). Y axis would be a duration of time, i.e over one year, over 10 years, over 100 years. Then it is a case of using the appropriate test to compare the two groups (null hypothesis being that the accident rate between two groups is the same). A fairly blunt measure granted. Given your experience with road accidents analysis, how would you approach it? _______________________________________________ Aus-soaring mailing list [email protected] http://lists.base64.com.au/listinfo/aus-soaring
