First day of vacation incident statistics
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Funny they would change that drastically in 15 years. Or the number is so small that a minor change in the raw data makes a big percent change in the "day of vacation."
Thoughts?
The 1994 percentage is based on 88 cases according to that link, the caycompass article mentions "it has analysed almost 1,000 files on dive fatalities to determine the root causes of these incidents".
Sure would be nice to have that DAN report from 2008.
Sure would be nice to have that DAN report from 2008.
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As I said, my source was an oral presentation (including PPT) from a DAN employee. It was presented as startling new information; it may have been based on recent raw and unpublished data. I am pretty sure I remember it correctly, but I have only my memory to guide me.
I remember it well because as soon as I heard it, I sat down and did some math. There is an old joke (sort of) among skiers: 100% of all serious accidents happen on the skier's last run of the day. (Of course! You don't make a run after a serious accident.) There is a similar statistical quirk related to diving and DCS. If you have a serious case of DCS on any day, you don't dive any more on that vacation. That fact alone would skew the statistics to the first day, with the second day coming in second, etc. Another quirk lies in the fact that people dive for differing numbers of days on vacations. Everyone who dives does at least one day. Some do two, fewer do three, even fewer do four, etc. Thus, if we were talking about pure probability, there should be more DCS cases on the first day of a dive vacation, but when I played with the numbers, I saw that the numbers I was given were still well above pure probability.
There was a thread about it back then, and one of the participants posited the theory that divers somehow develop some kind of an immunity to DCS over time, so multi-day divers are less likely to become victims as each day passes.
---------- Post Merged at 10:40 AM ---------- Previous Post was at 10:29 AM ----------
There is another statistical problem related to DCS analysis, and that is that DCS is very rare. If you only have a couple of cases a year in your study, a couple more cases one year, which can be the result of simply getting more reports that year, can cause a doubling of that percentage. It would be wrong, then, to assume that the risk of DCS was actually going up, since that difference could be a sampling quirk in a year the percentage actually went down. You really need larger numbers to draw meaningful conclusions.
I remember it well because as soon as I heard it, I sat down and did some math. There is an old joke (sort of) among skiers: 100% of all serious accidents happen on the skier's last run of the day. (Of course! You don't make a run after a serious accident.) There is a similar statistical quirk related to diving and DCS. If you have a serious case of DCS on any day, you don't dive any more on that vacation. That fact alone would skew the statistics to the first day, with the second day coming in second, etc. Another quirk lies in the fact that people dive for differing numbers of days on vacations. Everyone who dives does at least one day. Some do two, fewer do three, even fewer do four, etc. Thus, if we were talking about pure probability, there should be more DCS cases on the first day of a dive vacation, but when I played with the numbers, I saw that the numbers I was given were still well above pure probability.
There was a thread about it back then, and one of the participants posited the theory that divers somehow develop some kind of an immunity to DCS over time, so multi-day divers are less likely to become victims as each day passes.
---------- Post Merged at 10:40 AM ---------- Previous Post was at 10:29 AM ----------
There is another statistical problem related to DCS analysis, and that is that DCS is very rare. If you only have a couple of cases a year in your study, a couple more cases one year, which can be the result of simply getting more reports that year, can cause a doubling of that percentage. It would be wrong, then, to assume that the risk of DCS was actually going up, since that difference could be a sampling quirk in a year the percentage actually went down. You really need larger numbers to draw meaningful conclusions.
Ayisha
Contributor
Also with social media, everyone is much more aware of incidents than they were in 1994, including DAN. DAN primarily finds out about incidents when and if they're reported to DAN, but they apparently do check the social media when they can and ask SB's and others to inform them of incidents - that opportunity wasn't there in 1994.
Mike
Contributor
However you want to sort it out. Bottom line good advice is - first dive of your vacation, leave the camera on the boat, take it slow, and pay extra attention to your dive buddy.
victorzamora
Contributor
As rare as these incidents are, I think that your second scenario is possible. However, look at how the dive industry has changed over the last 15 years. I'm 22, have been involved with diving for 11 years, and have seen a MARKED decrease in how dangerous Scuba is presented. I remember viewing scuba diving as nearly an "extreme sport". With marketing nowadays, it seems akin to Solitaire or checkers: no skill required and little-to-no risk involved. A lot of people are becoming a lot more cavalier with diving. A lot more people are getting certified and then not maintaining or refreshing before a dive trip.
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