Setting landing direction (was: Perris double fatality)

[danielcroft 2]

I think we're reading way too much into the statistics at this point. I'm interested to see what people think of the statistic that 83% of fatalities were D license holders. Extrapolating a percentage into probability doesn't seem like a sound application of the figures to me.

For the record, according to page 19 of the February 2010 board meeting presentation(http://www.uspa.org/Portals/0/Downloads/February2010BoardPresentation.ppt), there are far fewer D license holders than there are A license holders. In fact, D license holders represent the smallest number of people. That doesn't mean that D license holders aren't making the most jumps but I haven't found any statistics to support or refute that from the USPA. It would be interesting to see a break down of the average number of skydives made per license. At that point we could actually start looking further into the idea that one license group was overrepresented in the the fatality statistics. On the face of it, I doubt that D license holders represent ~83% of skydives made but that's just an unfounded opinion (from a relative newb).

[davjohns 1]

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Anyone care to comment on the statistic that 83% of skydivers who died last year were D license holder?

The statistic, by itself, is near meaningless.
D License holders are generally the ones making more jumps.

Take a deck of cards. Shuffle it. Pick a card at random.

Every single time you pick a card, you have a 1 in 52 chance of picking the Ace of Spades. Every single time.

However, while it's possible that you could go hundreds of rounds and never pick the Ace of Spades, it's far more likely that eventually you will, regardless of what you may have been taught about "Gambler's Paradox." The ratio stays approximately the same averaged out over every round. Eventually you will almost certainly pick the Ace of Spades.

People with A licenses generally don't stay that way for very long. People with D license tend to stay that way for a very long time and accumulate far more jumps than they did as A licensed skydivers.

I think you made a leap of inference there and slightly missed the fine point of probability statistics. The deck of cards does not know how many times you have pulled a card. Neither does the Ace of spades. Every time you pull a card out of a fresh deck, your odds are 1:52. Every time.

In relation to your comment, an equal number of A, B, C and D licensed jumpers should die every year (given an equal number exists within each category). If there are more A licenses than others, there should be a greater number of dead A license holders at the end of each year.

For your argument to hold, the most prolific license in the sport should be a D license by the measure that 83% of jumpers hold a D license. I have done no research, but highly doubt that is the case. Even then, we are talking about pure probability without any consideration of skill, experience or maturity in the sport. If you factor those in, theoretically, D license holders would be the least likely to die per capita. The wind, ground, rig, etc. have no idea if it is your first jump or 10,000th. They don't care.

But what is the probability that you will NOT have pulled an ace of spades at least once after 1,000 attempts? (answer, 3.7 x 10^-9). Meaning that after 1000 picks you have 99.9999996% likelihood of having pulled at least one ace of spades.

That's mathematically correct. Now, apply it to skydiving. In order for the same rules to hold, death must be an inevitable outcome of skydiving in a certain number of jumps regardless of conditions, skill, judgment, etc. To apply the same logic as the deck of cards, death must be an equal probability as every other potential option.

In other words, why do we bother with training, testing, licensing, rules, etc. if we can not change the odds?

I looked over the reasons for death in the statistics. One of them showed that the person removed their rig during the jump (suicide). For the reasoning offered to hold, this must have been inevitable and not a choice. That card merely came out of the deck in it's statistically probable order. Jump long enough and you are just going to take off your rig regardless of any other factor.

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.

[kallend 1,623]

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Anyone care to comment on the statistic that 83% of skydivers who died last year were D license holder?

The statistic, by itself, is near meaningless.
D License holders are generally the ones making more jumps.

Take a deck of cards. Shuffle it. Pick a card at random.

Every single time you pick a card, you have a 1 in 52 chance of picking the Ace of Spades. Every single time.

However, while it's possible that you could go hundreds of rounds and never pick the Ace of Spades, it's far more likely that eventually you will, regardless of what you may have been taught about "Gambler's Paradox." The ratio stays approximately the same averaged out over every round. Eventually you will almost certainly pick the Ace of Spades.

People with A licenses generally don't stay that way for very long. People with D license tend to stay that way for a very long time and accumulate far more jumps than they did as A licensed skydivers.

I think you made a leap of inference there and slightly missed the fine point of probability statistics. The deck of cards does not know how many times you have pulled a card. Neither does the Ace of spades. Every time you pull a card out of a fresh deck, your odds are 1:52. Every time.

In relation to your comment, an equal number of A, B, C and D licensed jumpers should die every year (given an equal number exists within each category). If there are more A licenses than others, there should be a greater number of dead A license holders at the end of each year.

For your argument to hold, the most prolific license in the sport should be a D license by the measure that 83% of jumpers hold a D license. I have done no research, but highly doubt that is the case. Even then, we are talking about pure probability without any consideration of skill, experience or maturity in the sport. If you factor those in, theoretically, D license holders would be the least likely to die per capita. The wind, ground, rig, etc. have no idea if it is your first jump or 10,000th. They don't care.

But what is the probability that you will NOT have pulled an ace of spades at least once after 1,000 attempts? (answer, 3.7 x 10^-9). Meaning that after 1000 picks you have 99.9999996% likelihood of having pulled at least one ace of spades.

That's mathematically correct. Now, apply it to skydiving. In order for the same rules to hold, death must be an inevitable outcome of skydiving in a certain number of jumps regardless of conditions, skill, judgment, etc. To apply the same logic as the deck of cards, death must be an equal probability as every other potential option.

In other words, why do we bother with training, testing, licensing, rules, etc. if we can not change the odds?

I looked over the reasons for death in the statistics. One of them showed that the person removed their rig during the jump (suicide). For the reasoning offered to hold, this must have been inevitable and not a choice. That card merely came out of the deck in it's statistically probable order. Jump long enough and you are just going to take off your rig regardless of any other factor.

Nope. You misunderstand the concept of probabilities.

...

The only sure way to survive a canopy collision is not to have one.

[SethInMI 145]

Daniel, slide 19 of the Board Meeting shows new licenses granted, not total currently active.

Even though about 4x as many new As were issued as Ds, this still does not mean that there are 4x as many active As as Ds.

Skydivers stop skydiving at all license levels. What slide 19 says to me is many quit before they get Ds or even Cs. Slide 19 does not rule out the possibility that most active skydivers are Ds. I tend to break skydivers into 3 categories:

1. Casual Tourist. Quits before 50-100 jumps.
2. Dedicated Tourist/Casual Instructor. Quits before 400 jumps.
3. Dedicated Instructors. Long time worker builds 1000+ jumps. Also includes video flyers/competitors.

At my DZs, a rough guess would put the number of active jumpers in each category at roughly equal numbers, but that would be pretty rough guessing at two Cessna DZs. The majority of jumps done will be work jumps, and they will be done by the people in group 3.

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[davjohns 1]

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Anyone care to comment on the statistic that 83% of skydivers who died last year were D license holder?

The statistic, by itself, is near meaningless.
D License holders are generally the ones making more jumps.

Take a deck of cards. Shuffle it. Pick a card at random.

Every single time you pick a card, you have a 1 in 52 chance of picking the Ace of Spades. Every single time.

However, while it's possible that you could go hundreds of rounds and never pick the Ace of Spades, it's far more likely that eventually you will, regardless of what you may have been taught about "Gambler's Paradox." The ratio stays approximately the same averaged out over every round. Eventually you will almost certainly pick the Ace of Spades.

People with A licenses generally don't stay that way for very long. People with D license tend to stay that way for a very long time and accumulate far more jumps than they did as A licensed skydivers.

I think you made a leap of inference there and slightly missed the fine point of probability statistics. The deck of cards does not know how many times you have pulled a card. Neither does the Ace of spades. Every time you pull a card out of a fresh deck, your odds are 1:52. Every time.

In relation to your comment, an equal number of A, B, C and D licensed jumpers should die every year (given an equal number exists within each category). If there are more A licenses than others, there should be a greater number of dead A license holders at the end of each year.

For your argument to hold, the most prolific license in the sport should be a D license by the measure that 83% of jumpers hold a D license. I have done no research, but highly doubt that is the case. Even then, we are talking about pure probability without any consideration of skill, experience or maturity in the sport. If you factor those in, theoretically, D license holders would be the least likely to die per capita. The wind, ground, rig, etc. have no idea if it is your first jump or 10,000th. They don't care.

But what is the probability that you will NOT have pulled an ace of spades at least once after 1,000 attempts? (answer, 3.7 x 10^-9). Meaning that after 1000 picks you have 99.9999996% likelihood of having pulled at least one ace of spades.

That's mathematically correct. Now, apply it to skydiving. In order for the same rules to hold, death must be an inevitable outcome of skydiving in a certain number of jumps regardless of conditions, skill, judgment, etc. To apply the same logic as the deck of cards, death must be an equal probability as every other potential option.

In other words, why do we bother with training, testing, licensing, rules, etc. if we can not change the odds?

I looked over the reasons for death in the statistics. One of them showed that the person removed their rig during the jump (suicide). For the reasoning offered to hold, this must have been inevitable and not a choice. That card merely came out of the deck in it's statistically probable order. Jump long enough and you are just going to take off your rig regardless of any other factor.

Nope. You misunderstand the concept of probabilities.

Wow. Your informational cites and pure logic overwhelmed my reasoned arguments and experience. I give up. I'll also quit teaching math and stop doing statistical analysis for a living.

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.

[danielcroft 2]

Thanks for pointing that out Seth, I might email Jim at the uspa and ask what the approximate guess is on the active distribution and if there's any estimate on how many jumps are being made by each license group. I'm curious to see how those numbers line up.

Oh and lol @ DavJohns.