Isn't it time you went in?

I read recently some military instructors have in the region of 10,000+ jumps and I even seem to remember reading about some guy having 25,000+

If this is correct, these guys are presumably reaching the point where, statistically, they 'should' experience a double-mal.

It doesn't matter how experienced you are or how well you pack, or how good your rig is. If there's a statistical law of averages, for anything, that law will always hold true eventually.

Sure, anyone could experience a double-mal at any time, even on their first jump. But mathematical law dictates that the more jumps you make, the closer you will reach the 'average' number of jumps needed for a double-mal, and the more likely it is to happen.

Thus a jumpmaster with 5,000+ jumps is at far greater risk of a double-mal every time he or she jumps, than an intermediate jumper on 300+

This is a purely mathematical question, and will be best answered in a statistical way. It can't be answered by simply stating that someone with 25,000+ jumps will be more experienced at handling mals, even if they are. This is about 'acts of god', that will always happen every x number of jumps, no matter how experienced you are.

Discuss...

Right, I'm leaving for Empuria now for the Xmas boogie. Hopefully see you there...

Stastics is one thing, but there is no reason why they would be more at risk than someone with 1 jump. The reserve on their back is no more likely to malfunction because of their jump numbers.

Derek

It is purely because of statistics that the above statement is correct. This isn't a skydiving question, but one of mathematics. The law of averages state there WILL be a double mal ever x number of jumps. The more jumps you make, the closer you will reach the average and the more change there is of it happening to you. It's a mathematical law because it's fundamentally correct.

A reserve IS more likely to malfunction the higher the number of jumps that person has. Not because the rig is 'faulty', but because the law of averages holds true.

No, that's not right.

Each jump is an independent event and it doesn't matter how many jumps the individual had prior to it.

Look up "binomial" distributions in a statistics book and it'll clear things up for you. Simpler to look at flipping a coin as the example, just replace 50% with 1/25,000 (or whatever your odds were).

The number is about 1 fatality in every 10,000 jumps. It is an average. The reason that there is people with 25,000 jumps is that we routinely sacrifice virgins. How many jumps ya got?

Incorrect. Say for example the odds of a double-mal are 1/25,000.

If someone jumped once, their chances of a double-mal would be 1/25,000. If they jumped 10,000 times, they would have another 10,000 'chances' and would be more likely to be 'unlucky'.

If a roulette wheel has come up 'red' 45 times in a row, yes, statistically, the chances of another red on the 46th spin are the same as before. But in theory, it will be more likely to come up 'black', because otherwise the wheel wouldn't be adhering to the law of averages of being 'fair'.

I'm no mathematician either, but this one's been bugging me quite a while...

Quote

Incorrect

Bawaaaahaaaaaa....

You didnt get very good marks in stats at school did ya?

Let's do a thought experiment. I flip a coin. It comes up heads. The next time I flip the coin, is it guaranteed to come up tails? By your logic it must, but common sense says that no matter how many times I flip that coin, on the next flip the odds of getting tails is always 50/50.

This is the biggest error made in stats and is very normal. i.e., asking AFTER something happened - "Wow, what are the odds?"

At that point, the question is moot because it's after the fact. I'll try to find the text in Minitab here, but look up 'binomial distributions' in a text and you'll see what I mean. Or if you want to talk vaguely, consider that the 1 in whatever applies to all jumps, not just to the one guy.

You can't store luck (or bad luck). An unlucky streak does not entitle anyone to assume that Lady Luck owes them. But Vegas counts on that thinking every day.

Crap - my job is currently practical application of stats, but Kallend could likely explain it better in everyday language. And I teach this stuff at work often.

Edit: Yes, now that you mention it, the current job is tediously boring and I hate it. But this specific duty is only until August....

Quote

Let's do a thought experiment. I flip a coin. It comes up heads. The next time I flip the coin, is it guaranteed to come up tails? By your logic it must, but common sense says that no matter how many times I flip that coin, on the next flip the odds of getting tails is always 50/50.

Ok, but what if it came up 'heads' 600 times in a row? Wouldn't you think there was something wrong with the coin? The law of averages means that eventually it will have to come up 'tails', otherwise the coin wouldn't be 'fair'. The more flips you make, the more likely it will eventually come up tails.

>Thus a jumpmaster with 5,000+ jumps is at far greater risk of a double-mal every time he or she jumps, than an intermediate jumper on 300+ <

Statistics can only be used for the next jump. So both jumpers have the same odds.

This is the mistake that most gamblers make

Dammit.. did we all get the same stats teacher or something?

This mistake is also know as the gambler's fallacy, i.e., "when a person assumes that a departure from what occurs on average or in the long term will be corrected in the short term." Below is a good site that explains it fairly well.
http://www.nizkor.org/features/fallacies/gamblers-fallacy.html

Enjoy.
__________________________________________________

Quote

It doesn't matter how experienced you are or how well you pack, or how good your rig is. If there's a statistical law of averages, for anything, that law will always hold true eventually.

But mathematical law dictates that the more jumps you make, the closer you will reach the 'average' number of jumps needed for a double-mal, and the more likely it is to happen.

Thus a jumpmaster with 5,000+ jumps is at far greater risk of a double-mal every time he or she jumps, than an intermediate jumper on 300+

your logic is flawed. The person with 10,000 plus jumps has (all other things being equal besides jump number) the same chance of experiencing a double mal as does the first time jumper. When you consider other factors such as experience, i would even agure that this jumper as a MUCH lesser chance of going in than does the first time jumper.

Jumper number has no direct corolation to double mals. (all other things being equal such as experience/packjob/equipment/etc)

Quote

Ok, but what if it came up 'heads' 600 times in a row? Wouldn't you think there was something wrong with the coin? The law of averages means that eventually it will have to come up 'tails', otherwise the coin wouldn't be 'fair'. The more flips you make, the more likely it will eventually come up tails.

Very unlikely - But also note that 300 exactly is not 50% (more like 3.26% likely)

Cumulative Distribution Function

Binomial with n = 600 and p = 0.500000

x P( X <= x )
600.00 1.0000
500.00 1.0000
400.00 1.0000
300.00 0.5163
200.00 0.0000
100.00 0.0000

This doesn't really have anything to do with the topic, it's just a boring day and post whoring is fun.

Quote

Thus a jumpmaster with 5,000+ jumps is at far greater risk of a double-mal every time he or she jumps, than an intermediate jumper on 300+

You see, your understanding of stats and probability is simply wrong. the 5000+ JM and the 300 jump novice, have the same probability of having a double mal. Which, from the other info in your post you seem to believe is about 1/25000. So, 1st jump, or 50000th jump, you have a 1/25000 chance of a double mal.

Don Kellner of Hazleton, PA has over 34,000 jumps (and still jumping) He hasnt gone in.

Statistically speaking, I am no less likely to experience a double mal on my next jump (having 66 jumps) than he is at over 34,000.

Quote

The law of averages means that eventually it will have to come up 'tails', otherwise the coin wouldn't be 'fair'. The more flips you make, the more likely it will eventually come up tails.

The law of averages only really applies to sample sizes at or approaching infinity, i.e., you flip a coin forever, and in the end (which doesn't exist, this is forever mind you) 50% heads, 50% tails. Oh my god, I can hear the statisticians rolling in their graves...

This is the single most common misunderstanding of statistics. I have amused myself to no end with buggering people with such questions. The answer is very simple. "What is the probability that I will not experience a DMal for 35,000 jumps" and "What is the probability of a DMal on my next jump" are two completely different questions. The people with 35,000 jumps are no more likely to experience a DMal than you are, it's just that there are a lot less such people. This means that the chances of a person who is just starting to survive to 34,000 are comparably small, hence there are few such people (more likely because people quit skydiving, but that's an aside). Once you make it to those jump numbers, however, the original calculation makes no more sense.

Here's a very simple question. Let's say I've rolled a fair die 999 times and 6 never showed up. What is the probability I get 6 on the next roll?

1/6, of course.

Quote

A reserve IS more likely to malfunction the higher the number of jumps that person has. Not because the rig is 'faulty', but because the law of averages holds true.

Fortunately reserves are not affected by statistics. If they were, after 25,000 jumps, your next one would be fatal, but your 25,001th jump has no more chance of being fatal than your 1st, all other things being equal.

Also, someone with 25,000 jumps probably hasn't used their reserve on every jump, I hope anyway. If they have 50 reserve rides, that is only 50 chances of having a double mal. If someone with 1000 jumps has no reserve rides, the odds of them having had a double mal are 0 for those 1,000 jumps.

For every 25,000 reserve deployments, odds are that one will mal. Doesn't have to, but odds are one will. (I'm not sure about the 1/25,000 number).

Derek

Quote

The law of averages means that eventually it will have to come up 'tails', otherwise the coin wouldn't be 'fair'.

You fatal flaw is your belief that the universe is somehow "fair" or gives a crap about fairness
Hasnt anyone ever told you that life isnt fair?

Quote

You see, your understanding of stats and probability is simply wrong. the 5000+ JM and the 300 jump novice, have the same probability of having a double mal.

So a person with 2000 pack jobs and a person with 20 have the same chance of packing a lineover. Is that what you believe, really?

A coin flip is pure probability. A coin doesn't get any better at packing, does it? A coin doesn't get smarter, that is why the probability stays the same.

Quote

Oh my god, I can hear the statisticians rolling in their graves...

For some reason, I just rolled over in my office

This discussion isnt about mals brought about by human error, but rather those that happen just by random chance. Sometimes you do everything right and something goes wrong anyway. Those are the ones this discussion is dealing with.
A good pack job is a good pack job whether the packer has 20 or 2000 jumps. That same good pack job can still produce a malfunction for no good reason and its not more likely on the 20 pack job guy than it is on the 2000 pack job guy assuming good pack jobs all around