Night flying in the mountians in a cessna 150,

"Ron Garret" wrote in message
...
[...]
and have determined the number of trials (flights) in advance.

No. That statement is true regardless of whether N is known.

Knowing that your chances of having an engine failure are 1-(1-P)^N isn't
very useful information if you don't know what N is.

It's not a useful calculation for the purpose of this discussion.

That is a matter of opinion.

Tell me how I'm going to use the information then. Since you think it's so
useful.

No one knows before they've started flying how many flights they will
make
in a lifetime.

That is not necessarily true. My mother, for example, knows exactly how
many flights in GA aircraft she will make during her lifetime: zero.

For a person who will never make a flight in a GA aircraft, why in the world
would I consider at all how many engine failures she'll experience?

It's like trying to figure out how many live births I'll have in my
lifetime. Duh.

And just in case you're too dimwitted to extrapolate from this example
I'll spell it out for you: one can *decide* on the basis of this
calculation to stop flying after some number of flight because flying
more than that results in a cumulative probability of disaster that
exceeds one's risk tolerance.

Only if they make that decision prior to flying those hours. I haven't met
a single person who has ever done such an analysis of their flying career.
I doubt one exists.

If you can find me one, I'll stand corrected. Otherwise, you are without a
point (I'll refrain from any implication that YOU are dimwitted, just 'cause
that's the kind of guy I am).

Pete

In article ,
"Peter Duniho" wrote:

"Ron Garret" wrote in message
...
[...]
and have determined the number of trials (flights) in advance.

No. That statement is true regardless of whether N is known.

Knowing that your chances of having an engine failure are 1-(1-P)^N isn't
very useful information if you don't know what N is.

As I pointed out before (and will point out again later on -- watch for
it) it is useful because you can choose your risk tolerance and then
solve for N (assuming of course you know P).

It's not a useful calculation for the purpose of this discussion.

That is a matter of opinion.

Tell me how I'm going to use the information then. Since you think it's so
useful.

I just did, but here it is again: if you believe that the risk of an
engine failure on any particular flight is P1 and you are willing to
accept a lifetime risk of experiencing an engine failure at no more than
P2, then you can use these two numbers and the formula for cumulative
probability to solve for N. You can then choose to stop flying after N
flights.

No one knows before they've started flying how many flights they will
make
in a lifetime.

That is not necessarily true. My mother, for example, knows exactly how
many flights in GA aircraft she will make during her lifetime: zero.

For a person who will never make a flight in a GA aircraft, why in the world
would I consider at all how many engine failures she'll experience?

It's like trying to figure out how many live births I'll have in my
lifetime. Duh.

No, because in my mother's case the number is zero because she has
*chosen* to make it zero. (Perhaps I should have made it clear that I
am a pilot, and so my mother can, if she chooses, go flying with me any
time she wants.) Your analogy is faulty because you cannot choose to
get pregnant.

And just in case you're too dimwitted to extrapolate from this example
I'll spell it out for you: one can *decide* on the basis of this
calculation to stop flying after some number of flight because flying
more than that results in a cumulative probability of disaster that
exceeds one's risk tolerance.

Only if they make that decision prior to flying those hours. I haven't met
a single person who has ever done such an analysis of their flying career.
I doubt one exists.

Just because you are not personally acquainted with someone who has
chosen to avail themselves of the utility of this calculation does not
mean that such people do not exist. (And even if it were true that no
one in the world has availed themselves of this utility (which it isn't)
that would not prove that the calculation is without utility.)

If you can find me one, I'll stand corrected.

I very much doubt that. You seem not to have noticed, but we've
actually already done that experiment, and you stubbornly cling to your
position regardless.

Not only are you wrong, but you are clearly, demonstrably, and
self-evidently wrong. If you don't believe me, you can actually *do*
this experiment. Don't play the lottery or go flying until your engine
fails. Get a die. Pretend that rolling a six means your engine has
failed. Now ask yourself: are you more likely to roll a six if you roll
it once, or if you roll it 100 times? Clearly if you roll it once your
chances are one in six, and if you roll it 100 times the chances of
rolling AT LEAST ONE SIX in those hundred trials is very close to 1.
(0.99999998792532652 to be precise).

Otherwise, you are without a point

Whereas you seem to have one on the top of your head.

(I'll refrain from any implication that YOU are dimwitted, just 'cause
that's the kind of guy I am).

Hey, if the shoe fits, I'll wear it. Will you?

rg

"Ron Garret" wrote in message
...
[...]
I just did, but here it is again: if you believe that the risk of an
engine failure on any particular flight is P1 and you are willing to
accept a lifetime risk of experiencing an engine failure at no more than
P2, then you can use these two numbers and the formula for cumulative
probability to solve for N. You can then choose to stop flying after N
flights.

But making that choice is only useful, and only based on correct
information, if you make the choice prior to the first of N flights.

As I said, no one ever does that. It's absurd to base any discussion on the
idea that anyone does, and certainly on the idea that it's a common analysis
generally useful to pilots.

Pete

In article ,
"Peter Duniho" wrote:

"Ron Garret" wrote in message
...
[...]
I just did, but here it is again: if you believe that the risk of an
engine failure on any particular flight is P1 and you are willing to
accept a lifetime risk of experiencing an engine failure at no more than
P2, then you can use these two numbers and the formula for cumulative
probability to solve for N. You can then choose to stop flying after N
flights.

But making that choice is only useful, and only based on correct
information, if you make the choice prior to the first of N flights.

As I said, no one ever does that.

Not so. But it's pointless to argue with you and life is short.

rg

"Ron Garret" wrote in message
...
Not so. But it's pointless to argue with you and life is short.

You claim that someone does. In order to truthfully make that claim, you
would have to know of such a person. If you knew of such a person, it would
be trivial for you to say who that person is.

The only logical conclusion from your refusal to say who that person is, is
that you are untruthful when you claim that someone does.

As far as "arguing", well...if you're not willing to support your statements
with any factual evidence, I can see why you have such a low tolerance for
"arguing".

Pete

In article ,
"Peter Duniho" wrote:

"Ron Garret" wrote in message
...
Not so. But it's pointless to argue with you and life is short.

You claim that someone does. In order to truthfully make that claim, you
would have to know of such a person. If you knew of such a person, it would
be trivial for you to say who that person is.

That's right, it was.

The only logical conclusion from your refusal to say who that person is, is
that you are untruthful when you claim that someone does.

No, your premise is wrong. I have in fact already given you two
examples (and I have even pointed this out to you once already).

As far as "arguing", well...if you're not willing to support your statements
with any factual evidence, I can see why you have such a low tolerance for
"arguing".

I have a low tolerance for arguing with people who insist on knocking
down straw men. Good day.

rg

"Ron Garret" wrote in message
...
No, your premise is wrong. I have in fact already given you two
examples (and I have even pointed this out to you once already).

Really? I must have missed those posts. I don't recall you telling me the
name of anyone using the risk analysis you propose. But again, I am more
than happy to be corrected. Please feel free to point the posts out to
me...I will happily concede your point. Most convenient for me would be a
link to the Google Groups record of the post, but a Message-ID would be
fine.

Pete

Ron Garret wrote:
In article ,
"Peter Duniho" wrote:


"Ron Garret" wrote in message
...

[...]
I just did, but here it is again: if you believe that the risk of an
engine failure on any particular flight is P1 and you are willing to
accept a lifetime risk of experiencing an engine failure at no more than
P2, then you can use these two numbers and the formula for cumulative
probability to solve for N. You can then choose to stop flying after N
flights.

But making that choice is only useful, and only based on correct
information, if you make the choice prior to the first of N flights.

As I said, no one ever does that.


Not so. But it's pointless to argue with you and life is short.

rg

Okay, I haven't been following this thread much, but reading a few of
these, I think a number of posters are having serious problems with
probability. The posts by Peter Duniho that I've read, in contrast, do
seem to understand probabilistic reasoning.

Yes, someone could decide to limit their lifetime risk of an engine
failure to P2 by flying exactly N flights. But in real life such a
decision would be insane.

First, if you were to have an engine failure during those N flights, it
would almost certainly not occur on the Nth flight. Therefore people who
have an engine failure are extremely unlikely to ever reach N flights.

Second, for any real world value of N (say N=1000), the marginal
increase in risk for flying N+1 flights would be trivial. P2 is much,
much larger than P1. So having accepted the risk of flying 1000 flights
and having successfully completed them, to decide to stop flying just so
as to avoid passing some given lifetime P2 would be bonkers. Flying that
N+1 flight has a risk of P1, a tiny risk compared to the one the person
accepted (P2) in flying N flights.

--
David Rind

In article ,
David Rind wrote:

Ron Garret wrote:
In article ,
"Peter Duniho" wrote:


"Ron Garret" wrote in message
...

[...]
I just did, but here it is again: if you believe that the risk of an
engine failure on any particular flight is P1 and you are willing to
accept a lifetime risk of experiencing an engine failure at no more than
P2, then you can use these two numbers and the formula for cumulative
probability to solve for N. You can then choose to stop flying after N
flights.

But making that choice is only useful, and only based on correct
information, if you make the choice prior to the first of N flights.

As I said, no one ever does that.


Not so. But it's pointless to argue with you and life is short.

rg

Okay, I haven't been following this thread much

That makes two of you, apparently.

rg