Re: [Paddlewise] ACA Accident Report - Critical Judgment II

   Not only has "hours spent on the water" not been factored in, but as
you pointed out, there is no mention of total numbers of paddlers  
(dead and alive) in each experience class. Paddlers who did not die  
were "censored" out
of this study. This kind of data falls into the area of Survival Analysis,
a branch of Statistical Science. Survival analysis uses all the information
available from both fatalities and censored survivors, and allows concomitant
variables to be used as well, such as age, gender, etc. A good study of
paddler fatalities should be done by someone well-trained in survival
analysis. This is too specialized an area even for a good general  
statistician.
An analogous study would be examinating survival rates of cancer  
patients, where
all the data is utilized, both from patients who die, and patients who either
drop out of the study, or live beyond termination of the study.
   Another complicating factor to consider: suppose a paddler participates in
kayaking for 50 years, and at age 70 has a heart attack while on the water
and capsizes and dies. Will that count as an experienced kayaker fatality?

Brad

Quoting Dave Kruger <kdruger_at_pacifier.com>:

> Bradford R. Crain wrote:
>> According to the ACA Report, Table 13 below, roughly equal numbers of
>> novice paddler and experienced paddler fatalities were tabulated in this
>> study, giving the false impression that novice and experienced paddlers
>> are dying at the same rate. The counts have not been adjusted for total
>> hours of risk exposure per paddler, nor has the data been adjusted for
>> degree of severity of environment in which each paddler has been
>> operating. Clearly this data should be adjusted for total risk exposure,
>> just as a cancer patient would be. I find this table terribly
>> misleading.
>
> Excellent points, Brad.  Nor has it been adjusted for "paddler skill"
> in the face of difficult/dangerous conditions.  IOW, for a really
> skilled paddler, Class III WW is about as dangerous to that paddler as
> Class I is to a novice.
>
>> Table 13: Canoe and Kayak Fatalities by Operator Experience 1996-2002
> -----------------------------------
> |      Hours           | Per Cent |
> -----------------------------------
> |    <10 hours         |  29%     |
> -----------------------------------
> |   10-100 hours       |  39%     |
> -----------------------------------
> |   over 100 hours     |  31%     |
> Jeez, Brad, are you surprised they can't do math?  They had two PhD's,
> an MD, and a USCG "Boating Safety Statistician" on board for this
> report. [big, cheesy grin: we all know "PhD" stands for "Piled Higher
> and Deeper" in the hierarchy of "BS" and "MS" ("More of the Same");
> BTW, I are one of the piled higher and deeper ones, so I should know!]
>
> Their comment about this table _does_ suggest, in a backhanded way,
> that there is a higher than _expected_ rate for the novices:
>
> "Another risk factor for mishap and injury among paddlers is
> inexperience. Information on experience is only available for 323 of
> the 574
> known canoe and kayak fatalities in the USCG database. The majority of
> these fatalities had more than 10 hours of experience (71%) with
> just less than a third reporting more than 100 hours of experience
> (Table 13)."
>
> I think they are trying to say that, other things being equal, you'd
> _expect_ a much higher rate of fatalities among more experienced
> paddlers, because of greater risk exposure, but the rate for novices is
> _as_high_ as that for experienced paddlers.  Meaning:  if novices were
> better trained in really basic safety practices, their rate should be
> lesser than the rate for folks exposed for longer periods of time to
> more risky conditions.
>
> Yeah, yeah, I know.  They did not compare the number of fatalities to
> _how_many_ folks were in each group, or to the number of hours of
> exposure/paddler.
>
> A better table would have been one which compared "deaths per
> paddler-hour on the water."  Probably they had no way to get at that
> figure, except conjecture.  Not to mention that there are no experience
> data for some 40% of the 574 known fatalities.
>
> In the end, I think the focus should be on "stupid deaths," in which we
> identify deaths that are easily prevented and get folks to avoid doing
> stupid things like boating drunk.  And, then, accept that in any risky
> activity, some people are going to freaking die!!  Life is short.  As
> Janis Joplin said:  "Get it while you can ..."
>
> -- 
> Dave Kruger
> Astoria, OR
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