josh_ingu:
OK. Good. Lets not however assume that other people also do not have similar experience.
Now, the original "cut and paste" was comparing the *relative risk* of activities. I agree that no values were given (man hours/days weeks), and no odds ratios were given either, as were no absolute values. In this case, however, we *can* assume that, as its a comparison, the "units" were the same. There is no reason to assume that diving was calculated in "seconds diving" and being a passanger as "man years in a car", otherwise it *would* be impossible to compare. So, for us to assume that the calculation was done in terms of "time per activity" is fair and sound (in the absence of further data).
According to the statistics professor who was on my PhD committee, the first rule of data analysis is: “Hell hath no fury as an unwarranted assumption.”
josh_ingu:
That being said, however, the main problem in this thread is the "throwing the baby out with the bath water." What *solid* data there is, gets cited when it supports our arguement, and trashed when it does not. Thalassamania says that as we dont have *full* data, then we can't trust *any* data.
I don’t think I said that.
josh_ingu:
Is that correct? Well, no. Of course it is not. Statistsics is, largely, about analysis of incompete data sets to enable us to draw conclusions about the whole data set with a certain degree of assurance (remember that bit fisherdvm?).
You need some more statistical training than you have received to date. Statistics is ENTIRELY the analysis of COMPLETE sample data sets to enable us to predict the makeup of larger sampled populations. Incomplete data sets and poor sampling design make for bogus statistics and can only be viewed, at best, as exploratory data analysis. You should read Tukey’s book on the subject (Tukey, John (1977), Exploratory Data Analysis, Addison-Wesley).
josh_ingu:
So, what data *do* we have?. We have, with a certain degree of assurance
1. The number of reported accidents per year. Now is this *all* accidents per year? No of course not. Is it a "selected set" of data? To a large degree, yes. Between years, is there *any* evidence that the percentage of all accidents reported, or the *type* of accidents reported varies significantly? No, there is no evidence that the percentage of all accidents, or the type of accidents reported changes. So we *can* use this data as at least *representative* of the number/type of accidents in diving each year.
No there is no basis to make that assumption, factored into that would have to be changes in standards, effects of shifts in numbers trained under one set of standards vs. another, effects of changes in equipment and the way in which equipment is used, etc. There are too many items that are not held constant.
josh_ingu:
2. The second type of data we have is the number of certifications each year. Do we have *exact* data on all certifications every year, and does anyone collate the various organizations together to provide a total number of certifications each year? No. Can we use, say, *one* organization as a guide? Yes, again, in the absence of data that says that that organization does something *markedly* different from other organizations that affects year to year reporting, we could use the data from one organization to give us an *idea* of where the whole market segment is going.
No this data is unavailable and has been unavailable from day one. There is not even corroborated data from a single organization.
josh_ingu:
OK. We have two *representative* pieces of data. Neither set is *complete*, and both sets are merely representative of the whole of the diving industry. Both sets *are* however relatively "solid" numbers.
So your going to draw sweeping correlations, without even a reasonable theory of causality, based on comparing two incomplete (and potentially intentionally skewed) possibly non-independent variables.
josh_ingu:
From those two data sets it is clear, despite any thing else going on that diving is getting SAFER. This is explicitly stated by DAN, and there is no evidence *anywhere* to the contrary.
Safe means “without risk,” this is clearly not the case. If you had valid samples you might be able to talk about reduced vs. increased risk. But the data is not even good enough for that.
josh_ingu:
That, frankly is just sad. Some one who bases their opinion on no data, or upon no factual basis is not an "expert". They are, at best, a good guesser and at worst a blowhard. To provide a convincing arguement, one that will convince the doubtful - you need DATA. Real data, and not "I guess".....or "I think......." or "I believe....".
Again, you have no idea of what you are talking about. In the face of inadequate data often the best analysis is that provided by the integrative power of the human mind once exposed to all the data.
Unlike you, (who is shooting in the dark, I guess that’s where your knowledge of the “blowhard” approach comes from) I had the advantage, at the behest of the U.S. Coast Guard, NOAA and OSHA, of reading each and every case file from the National Underwater Accident Data Center. My professional conclusion at the end of that process was that no valid statistical analysis could be performed on the data and that it’s value (with one notable exception that I’ll discuss later) lay in, not in rather poor attempts that had been made to quantify, but in the strength of the accident narratives wherein divers could “experience” accidents without having to actually go through them. The exception was the peak in accidents and training fatalities in the later 1970s that seems to have been reduced by PADI putting an end to their policy of certifying (with nothing more than paperwork) anyone with a claim to have taught diving in the past and cleaning house by creating the distinction between a PADI Diving Instructor and a PADI Openwater Diving Instructor. That change, which was brought about as a result of the NUADC’s identification of the problem, seemed (coincidentally?) to result in turning around the growth of training fatalities and actually reducing them. I guess that’s what you mean by a “good guess?”
josh_ingu:
As a side point, it would be interesting to know the basis by which Thalasamania proposes that DAN are "self-serving". They are in the buisness of selling dive insurance. It would be more in their interest to make diving out to be more dangerous (to sell more insurance) rather than *less* dangerous.
Because I know the industry, because I’ve been witness to the conversations in the “smoke-filled” rooms where the deals are made. Because I know the people involved and have been a confidant of some of them. DAN is not in the business of selling insurance, they are in the same certification business as the agencies. DAN would like to appear to be the “Red Cross of Diving” but has, in the past, engaged in some rather bizarre, shady and self-serving deals. I have complete confidence in the new leadership there, especially Dan Orr, and I fully expect the past abuses, sweetheart deals and the cronyism attitude that went with them to end.
josh_ingu:
... as thats the easiest to tackle. Ecologically, that habitat destruction due to divers is gonna be relatively easy to quantify - if you are prepared to put some time and effort into it. Get some 1 meter length wooden slats, make them into squares (PVC pipes would do as well). Pick two areas, one frequented by the type of diver you think are a problem, one not (for whatever reason). You want those two areas to be as similar as possible, with the only variable being the divers in one. Put the square down, and *count* the number of your indicator species (nests/eggs whatever). Do that over as long as you can, as regularly as you can. Two season? Three? Now, at the end of your study, *compare* your two data sets. Now you can start to say "divers in this area are impacting significantly, indicator species show a XY% reduction in ..... blah blah blah". You could video actual divers impacting upon the dive environment to enfoce your point. Get your divers (and students) involved. Underwater photography, videography, marine concervation, underwater naturalist etc etc all rolled into one neat little ball. From what I recall, Thalassamania is supposed to be some sort of Marine biologist or other, he could be giving you far more pertinent advice on how to *document* the habitat destruction than I can. If you start from a position of *real* data, people *are* going to listen to you. Ranting on boards like this may be fun, but, in the final analysis, its rather pointless. So, Mike, do you wanna blather on about standards, or do you want to *do* something? Your call.
There is no need to waste resources studying the obvious. I suspect that all parties involved will stipulate to the habitat destruction. We are currently facing much more critical problems to which our scientific resources need to be applied.
Please, take two aspirin, three deep breaths … and call us after you’ve read Tukey’s book.
