...Nereas, as you've suggested, I would contended that you are realying more on anecdotal evidence than scientific method. Vplanner, which I use and trust, is a theoretical model, trying to predict the possible outcome. And, while many dives have been safely conducted using it, I don't believe the actual study of those dives comes anywhere near what has been done with the USN tables. Furthermore, the body of dives that have been studied are those submitted by divers themselves, hardly a poster child for objective scientific method. Is Vplanner based on science? Yes, theoretical body chemistry and physiology. Has it been well tested by objective scientific method? I'm sure Ross could inform us to what extent. But, probably not as thoroughly as the USN tables. However, we hear good things about the outcome of Vplanner(and other newer softwares) dives and based on those anecdotes choose to use it.
The USN tables are probabalistic in their nature. Take a bunch of young men, put them at depth for a time, surface. See how many get bent, determine the standard deviation, adjust to provide an acceptable probability of DCS(very low). They're based on thousands of objective dives. And arguably are supported by a less anecdotal method.
I'm not pro USN tables(although we do carry a foldable set in a pocket as a SHF contingency), nor am I opposed to Vplanner(on the contrary I use it and think it's one of the better planning programs, with one of the better user interfaces). I'm just trying to point out that the tendency to dive in what might be considered a more conservative manner, longer deco curves and lower END, may in fact be based on more anecdotal evidence than the the conventional methods. That was certainly the way that nitrox came to prominence and is the by and large the way helium is working it's way into sport or recreational diving.
So, Anecdotal evidence is neither good nor bad. It just has to be treated accordingly.
Since I am no longer a "young man," I have long since concluded that the USN tables are inapplicable to me, because the data base from which those tables are derived are not comprised of anything taken from "old men."
And since V-Planner allows me to jack up (nautical term) the conservatism features, and because +3 has been giving me great results on my deco dives so far (anecdotal), I intend to use it until I am too old to put on twin tanks and roll off a boat, or climb back up the ladder, anymore.
Chickdiver-Heather was the first person here on ScubaBoard who mentioned V-Planner to me, anecdotally, to give credit where credit is due. We were discussing the new NAUI RGMB deco tables at the time. Those have odd requirements, however, such as chopping an entire ATA off your previous deco dive to plan a subsequent one. That is problematic when the shipwreck does not cooperate and raise itself for you by an equivalent 33 fsw.
So, as I said, anyone who wants to be a techdiver needs to be armed with as much anecdote as can be gleaned. Too many techdivers have died unexpectedly, and nobody wants to be the next one to die accidentally. The science alone is just not that good, yet (as I suspect NetDoc-Pete would agree).
My definition of anecdote from a technical perspective is to test everything one small step at a time with the body that your God gave you. Each season, as you get older. Whenever I do this, I am doing it to establish more conservative limits for myself, however, rather than to push the limits, which is how others have apparently defined anecdotal for themselves.
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an·ec·do·tal
–adjective 1.pertaining to, resembling, or containing anecdotes. 2.(of the treatment of subject matter in representational art) pertaining to the relationship of figures or to the arrangement of elements in a scene so as to emphasize the story content of a subject. Compare
narrative (def. 6). 3.based on personal observation, case study reports, or random investigations rather than systematic scientific evaluation: anecdotal evidence.
[Origin: 1830–40;
anecdote +
-al1
]
