Is anecdotal evidence dangerous?

[Thalassamania]

Another anecdote I see. The term SWAG came from WWII era scientists and possibly the Manhattan project in particular (though I have no corroborating evidence). I know for sure that I didn't invent the term, but I sure see a LOT of scientists and pseudo-scientists use them with little to no thought as to what they are doing.

It's not the invention of the term, that's been arround a long time in many forms (e.g., silly wild *** guess; Still Wondering and Guessing; etc.). It's your application of that term to Bob Workman's breakthrough development of M-Values and modeling decompression in a single equation that I find incredibly disrespectful on your part.

 

[The Chairman]

What about the testimonials on the Spare Air site?
Are they anecdotal evidence?

All of them are anecdotes by definition and they are indeed used to show the efficacy of diving with Spare Air. They also show us just how unsafe some divers are. However, there is no way to draw a conclusion that Spare Air or those who use it are unsafe without using such anecdotal evidence. That would be a biased sample fallacy.

 

[The Chairman]

It's not the invention of the term, that's been arround a long time in many forms (e.g., silly wild *** guess; Still Wondering and Guessing; etc.). It's your application of that term to Bob Workman's breakthrough development of M-Values and modeling decompression in a single equation that I find incredibly disrespectful on your part.

Apparently, I don't worship science as you seem to do. Tables and computers are merely tools, and the FIRST thing you do with any tool is to determine it's limitations. Are you implying that there are no limitations to this tool?

 

[fweber]

Diving in the U.S. Navy: A Brief History

Navy Diving | History

NavyDiver.org - History

DivingHistory.com - Evolution of Navy Diving

Four interesting articles. The basis for the Navy tables, was of course Haldane's work with goats. Stilson just changed the subject of the study.

Study of Goats= Non-anecdotal
Study of Pigs= Non-anecdotal
Study of Humans=Non-anecdotal

Applicable to recreational diving? Maybe, Maybe not. But, definately not anecdotal.


According to Oxford English,

anecdote: noun 1 a short entertaining story about a real incident or person. 2 an account regarded as unreliable or as being hearsay.

anecdotal: not necessarily true, not back up by facts

Netdoc, while you may agree or disagree with the accuracy or applicability of the studies, at least acknowledge that they make use of factural evidence as opposed to anecdotal.

If you can't do that, there is little purpose in continuing to discuss any of this with you.

 

[The Chairman]

If you can't do that, there is little purpose in continuing to discuss any of this with you.

I will agree with you: they are not in fact "anecdotes". They are comparing apples to oranges, or goats to humans as it were.

One of the first evidences of "bubbles" as being a part of DCS was a researcher (Haldane, I believe) seeing a bubble in a serpents eye that he had just decompressed. Is this an anecdote, a data point or both? As was pointed out, any dive whether it resulted in an incidence of DCS or not, is merely an anecdote. Combine a number of these together and we have a "study".

The real problem is the extrapolation of these data points.

One person has claimed that they bounced to 165 fsw and had no effects. Can we extrapolate that data to everyone? What if we had a thousand young and fit divers bounce to 165 fsw? Would no DCS provide us incontrovertible proof that a dumpy 45 YO would have no problem bouncing to 45? No, now it becomes a SWAG. How about if the water is 20 degrees colder than the sample? What if... (put your own variable here)???

The real problem is not the anecdote, but the fallacious conclusion drawn from the data at hand. If I said I did a half hour dive to 60 foot and did not suffer any symptoms of DCS, this would not only fall within the traditional data (as defined by the tables) but it would also be an anecdote for me to go on. It's the anecdotes that seem to DEFY our understanding of decompression physiology that disturb us the most.

 

[fweber]

So, back to the OP's question about, "Is anecdotal evidence dangerous?"

We've agreed that scientific studies may or may not be safe or applicable to recreational diving. But, at least we hope that they are done in a controlled and objective manner.

As to anecdotes. The OP seems to believe that they are, in fact, dangerous. While I think several of us believe them to be nothing more than additional data points, that require more careful consideration before use in a decision making process.

Very frequently, strong anecdotal evidence is what leads to the adoption by a larger user base and further research that can provide factual support for a particular idea or practice. Within recreational diving the three most notable and recent cases being, the use of Nitrox to extend NDL's at shallow depths, the safe use of Helium during bounce dives, and the adoption of deep stops while ascending from decompression dives. All spread due to largely anecdotal reasons. The major agencies were not initially pushing for such, scientific studies were not being funded to further the cause, a large portion of the supporting factual research has and is being done in an ex post facto manner. We have a brave few to thank for providing their anecdotes that have led us down these roads.

Now, we have additional anecdotal tales to consider: ratio deco, sacrificing NDL time and direct ascents to the surface in favor of END's of 100' and less, etc, time will tell whether these and other anecdotal stories find sufficient readers to gain favor and eventual factual support.

Anecdotal evidence is neither safe nor dangerous, it's someone's tale, take it as such, consider who is telling it, and what their experience level is or has been. I tend to not follow the advice of the extremely youthful, or those who are obviously following a path through life very different from the one I wish to travel. But, that doesn't mean I don't listen to it............

 

[Couv]

I have read so many posts that use only anecdotal evidence to support a particular point of view. To me this is down right dangerous in some cases. When it comes to diving, I see this as very troubling. How many times have we all read “ I’ve been to 160’ fsw on air and did fine” or “I came up from 100’ and did not do a safety stop” or “I don’t get narcked at 120’ fsw”. This sends a message that if I did it, you should be fine so go ahead and try it! I am always dubious when the only evidence is anecdotal.

I believe in the premise that science trumps anecdotal evidence every time. This not to say some have in fact done some of these things but is it safe for anyone, no. So when someone presents a situation where the only evidence is anecdotal, do more research before trusting the information.


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Is there such thing as the Diver's Darwin Awards? It might make an interesting sub-category to Accidents and Incidents.

 

[The Chairman]

Is there such thing as the Diver's Darwin Awards?

Not on this Forum and there WON'T be. We don't need MORE condescension than we already have.

 

[Couv]

Not on this Forum and there WON'T be. We don't need MORE condescension than we already have.

You ain't no fun. :mooner:

 

[The Chairman]

You ain't no fun. :mooner:

It would just lead to flame fests. We certainly don't need that here!