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**PhilSiswick** · 28th April 2008, 10:24

Quote: (Originally Posted by Christoph)

My problem with this discussion is that we have no way to tell for what kind of and how many dives the units are normally used. Thus all the -very earnest- approaches at calculating a risk factor per unit seem to me rather futile, even if and when we had all other relevant data.
Personally, I bought the HammerHead to ultimately be able to do dives I can´t do now with my rather elaborate trimix OC equipment. A year of accident free deep/long/cold/... "tec" dives would show up in this statistic with the same weight as my first (this) year on a rebreather with only shallow/no deco/normoxic dives is going to count.
I still believe that collecting and publishing all available data is a good thing and will improve our ability to identify fields of possible improvement and risk factors when diving a rebreather but from a mere statistical point of view I´d rather not try to calculate a number representing risk/unit.

I agree with this. If you further add the mods that people make which, in some cases take the unit a long way away from the manufacturer's design (HH on an Inspo for example), the data you need to get a meaningful risk/unit figure becomes greater.

It's a classic example of someone seeing numbers in a spreadsheet, applying some formulas and coming up with an answer. In the process of adding all the variables, they find that they don't have information to support some (units in use, average dives per year etc.) so they make some 'educated' guesses and eventually come up with a number. It's probably about as meaningful in this case, what with all the factors that have been highlighted, as plucking a number out of your lower torso. Oh sorry, I've just dammed Statistics

I'm all for the information getting out - I'm less in support of the statistical analysis.

Cheers,

28th April 2008, 10:24	#519 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,095	Re: Comprehensive list of all accidents Quote: (Originally Posted by Christoph) My problem with this discussion is that we have no way to tell for what kind of and how many dives the units are normally used. Thus all the -very earnest- approaches at calculating a risk factor per unit seem to me rather futile, even if and when we had all other relevant data. Personally, I bought the HammerHead to ultimately be able to do dives I can´t do now with my rather elaborate trimix OC equipment. A year of accident free deep/long/cold/... "tec" dives would show up in this statistic with the same weight as my first (this) year on a rebreather with only shallow/no deco/normoxic dives is going to count. I still believe that collecting and publishing all available data is a good thing and will improve our ability to identify fields of possible improvement and risk factors when diving a rebreather but from a mere statistical point of view I´d rather not try to calculate a number representing risk/unit. I agree with this. If you further add the mods that people make which, in some cases take the unit a long way away from the manufacturer's design (HH on an Inspo for example), the data you need to get a meaningful risk/unit figure becomes greater. It's a classic example of someone seeing numbers in a spreadsheet, applying some formulas and coming up with an answer. In the process of adding all the variables, they find that they don't have information to support some (units in use, average dives per year etc.) so they make some 'educated' guesses and eventually come up with a number. It's probably about as meaningful in this case, what with all the factors that have been highlighted, as plucking a number out of your lower torso. Oh sorry, I've just dammed Statistics I'm all for the information getting out - I'm less in support of the statistical analysis. Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
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