Isn't it time you went in?

[Push 0]

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Ok, but what if it came up 'heads' 600 times in a row? Wouldn't you think there was something wrong with the coin?

Either something is wrong with the coin, or you're very very special.

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[benny 0]

ahh. i have it now.... within any given year your chance of dying in a car wreck are about 1/6000.... how many times have you gotten behind the wheel... ooh, you gonna die man!

Never go to a DZ strip show.

[Blahr 0]

I could use a coin like that

[benny 0]

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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.

Well now, we actually never discussed the experience or skill of the packer... Which think for the reserve, and hence, double mal situation, that doesn't really apply as they have to be done by FAA certified riggers right? Umm, anyway, under your argument the more experienced person probably has a lower likelihood of a double mal. I'd say I tend to agree with you. That doesn't help the lark's argument though. What was your point again?

Never go to a DZ strip show.

[happythoughts 0]

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This discussion isnt about mals brought about by human error, but rather those that happen just by random chance

I guess that is my point. I believe that most mals happen for a reason, not random chance.

[wallygator 0]

what are the numbers of having a douvle mal into a fatal if the student is on exit number 6?

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who Jah bless Let no man curse.

[mjosparky 3]

Your main and reserve do not know how many jumps you have. You have the same chance of a double mal. on your first jump as you will have on you 10,000.

My idea of a fair fight is clubbing baby seals

[happythoughts 0]

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under your argument the more experienced person probably has a lower likelihood of a double mal. I'd say I tend to agree with you. That doesn't help the lark's argument though. What was your point again?

My point? The original question, why doesn't a guy with 25000 jumps have a double mal, because of statistics? My answer because it is not pure statistics. Coins don't improve.

As people become better drivers, they have less accidents. Most of the accidents are with inexperienced drivers.

In our case, packing accidents. To make an average, there is a newbie out there today chopping his improperly packed main while an experienced guy is doing his 500th consecutive ok opening.

I have line twists every 80 jumps. Average may (guessing) be every 40. There is a new guy getting them every 5. It makes the average 40, but my number is getting larger because of experience.

[benny 0]

I understand your point and agree happy, however, I was simply pointing out that even if it had everything to do with statistics, skylarks reasoning was wrong. If you read the lark's original post, he said he was asking a mathematical question. Or, maybe more correctly a question about the nature of probability. But, I digress.

Never go to a DZ strip show.

[DJL 232]

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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.

Guys, very important note here from Hook. This is why you should forge jump number 25,000.

I think this is my favorite thread of all time.

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[Reginald 0]

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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...

I'm a statistician my friend. Don't quit your day job. :)

"We've been looking for the enemy for some time now. We've finally found him. We're surrounded. That simplifies things." CP

[AndyMan 7]

Statistics tell us that we'll have a malfunctioning main canopy that requires a cuttawa roughly around every 1000 jumps. There's a pretty good track record of data to back that up, too.

We have absolutely no idea statistically speaking how often a reserve will fail. The isolated cases of it happening are so rare, that a statistical analysis is meaningless.

People frequently make the mistake of assuming that a reserve failure occurs at the same frequency as a main failure. Of course, we know this is absurd, because of the care taken in inspecting and packing that reserve.

We simply are unable to statistically analyse the failure rate of reserves. There are too few reserve rides, never mind reserve failures to do this.

If we can not estimate the failure rate of reserves, then we can not estimate the failure rate of double malfunctions. We can't even guess. We can't extrapolate based on main malfunctions - there simply is no co-relation. We have no idea.

We know its a small risk, but thats it.

Secondly, ignoring all that.... What if we did do the impossible, and figured it out? Hypothetically, what if we decided that the rate is 1 in 50. Obviously this number is wrong, but lets use it. In this example, 1 in 50 skydives result in a double failure.

If you have zero skydives, the odds of a double malfunction on your next jump is 1 in 50. On your second jump, the odds are still 1 in 50. On your tenth jump, the odds are STILL 1 in 50. Indeed, on your fiftieth jump, the odds are still 1 in 50. If we've analysed the risk properly and controlled all other variables, the risk on every jump is exactly the same. The risk does not increase the more jumps you do.

For that reason, it is not the case that someone with 50,000 jumps is "due" for a double malfunction. The statistics only indicate the odds of it happening on his next jump.

Thirdly, its important in skydiving that we be aware of the risks to us, in order to avoid them. On my list of fears, an "act of god" double malfunction is not very high on my list of priorities. I'm much more concerned about a double malfunction that I caused, such as by deploying my reserve into my malfunctioning main, an entangled main that won't cuttaway, etc. A review of recent fatalities shows precious few people going by way of "acts of god". Far too many people go in because they made poor choices, or responded poorly to a problem they could have fixed.

I am much more concerned about the parts of skydiving that I can control, rather than those I can't.

_Am

__

You put the fun in "funnel" - craichead.

[CrazyDave 0]

we have heard this type of thread so many times... and as has been said before, the statistics are one thing, but the presence of reall world variables and other constants greatly effects the 'statistics' accuracy.

[markbaur 0]

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Statistics tell us ...

that you're more likely to have a malfunction on your next jump than to go any number of additional jumps and then have a malfunction.

It gets worse. You're also more likely to have a double malfunction on your next jump than to go any number of additional jumps and then have a double malfunction.

Ain't statistics grand?

Mark

[FrogNog 1]

A person with 25,000 jumps and a 1 in 25,000 chance of having a double-mal on any one jump does not have a "1 in 1" chance of having had a double-mal in those 25,000 jumps. Probability is not additive like this, it is multiplicative. Probability also never resolves to an absolute until it has happened; while it is still theoretical, probability is always probability.

The probability that the military instructor mentioned will NOT have a double-mal is 24,999 in 25,000. The probability that the military instructor will NOT have a double-mal on two jumps in a row is 24,999 * 24,999 in 25,000 * 25,000. After 25,000 jumps the probability that he will not have had a double-mal anywhere in there is 24,999 ^ 25,000 in 25,000 ^ 25,000.

Can anyone work that number out? My calculator doesn't work with numbers that large (or small) very well.

Statistics doesn't ever say something should happen. It says how often it has happened, and based on that how often it is likely to happen in the future.

Statistics / probability are also exercises in "sampling". We look at how many jumps in a large pool happened and how many d-mals there were, and we come up with a probability that is applicable to that entire sample, in the long run. When that probability is applied to a different sample, there will probably be some mismatching. I believe this is what "average and standard deviation" are all about: describing how well the centerpoint fits the sample overall.

-=-=-=-=-
Pull.

[twnsnd 1]

This is one double mal in every 25000 jumps made, not by an individual, but by all jumpers. You could have a million jumps and all the mals could be happening to someone else.

-We are the Swoophaters. We have travelled back in time to hate on your swoops.-

[DJL 232]

Can we move this one to Talkback? I'm really having trouble biting my tongue.

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[PhillyKev 0]

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It is purely because of statistics that the above statement is correct. This isn't a skydiving question, but one of mathematics.

Your statement has absolutely nothing to do with mathematics except to demonstrate a misunderstanding of it.

[newsstand 0]

When they go for the world record 25,000 way there is a high probablity that one person will have a dmal.

"Truth is tough. It will not break, like a bubble, at a touch; nay, you may kick it about all day like a football, and it will be round and full at evening."
-- Oliver Wendell Holmes

[fool 0]

Just a point here. This site is filled with post after post of people telling others to seek out skydiving advise from those with more experience, and listen to them. I'd say the same goes for statistics. There are many sources of information available here, only useful if you heed them. if this many people are saying you are wrong, you're probably wrong. too bad you're wrong though, I'd just wear a tertiary reserve on 25000 and save my ass.

S.E.X. party #1

"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "f*#k, what a ride".

[Squeak 17]

From my limited understanding on Stats.
the 1/25000 is applied to ALL jumps everywhere.
you can get 50,000 jumps easily and not be affected by the average because it may not be you who has the D/Mal.
So theorehtically you could do 1,000,000 jumps and as long as 40 someones have DMals then the stats still hold true.

You are not now, nor will you ever be, good enough to not die in this sport (Sparky)
My Life ROCKS!
How's yours doing?

[firstime 0]

if it's not stupidity or incompetance it's called FATE

[sdgregory 0]

Squeak nailed it there.


On the other side of this is that God can overcome any mathematical statisitic. I will not worry about a double mal. If God wants me to have one than I will have one and if He doesn't I won't.

Either way I end up back in the sky after my landing!

[msmithd8769 0]

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If you flip a coin you have a 50/50 chance of getting heads right? If you flip it again after getting tails what are your odds? 50/50.

So, if you have a 1 in 25000 chance of a double mal and you do a jump - what are the odds the 2nd jump you do? Still 1 in 25000.

I'm no math wizz, but as far as I know your odds stay the same for every jump, regardless of the statistics.

EDIT: Crap...remwha beat me to it.

Blue skies
Ian

You are correct. The same argument was made many times by pilots in WWII who would become more and more afraid that their "number was up" the more missions they flew. They figured the odds were going to catch up with them and that they had more of chance being killed the more missions they flew. In actuality their risk factor is the same on every mission and they had no higher a chance of being killed whether it was their first or 50th mission. Holding all other factors the same, the number of missions made no difference.....

_____________________________
"And when the prophet shall arise who appeareth as a bird then the time of the Lord draweth nigh and the flock shall rule the earth."

[nightjumps 1]

Exactly right. Normally referred to as "Gambler's Fallacy."