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Absence of Evidence
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yak52

Joined: 25 Oct 2007
Posts: 50

Posted: Thu Feb 26, 2009 12:13 pm Post subject: Absence of Evidence

In probability theory, absence of evidence is always evidence of absence.   If E is a binary event and P(H|E) > P(H), "seeing E increases the probability of H"; then P(H|~E) < P(H), "failure to observe E decreases the probability of H".  P(H) is a weighted mix of P(H|E) and P(H|~E), and necessarily lies between the two.  If any of this sounds at all confusing, see An Intuitive Explanation of Bayesian Reasoning.  

Under the vast majority of real-life circumstances, a cause may not reliably produce signs of itself, but the absence of the cause is even less likely to produce the signs.  The absence of an observation may be strong evidence of absence or very weak evidence of absence, depending on how likely the cause is to produce the observation.  The absence of an observation that is only weakly permitted (even if the alternative hypothesis does not allow it at all), is very weak evidence of absence (though it is evidence nonetheless).   [quote][b]

notsew_evets(at)frontiern
Guest

Posted: Thu Feb 26, 2009 12:28 pm Post subject: Absence of Evidence

So,  in reality Abstinence is bad  ?

 [quote]   ---

jaybannist(at)cs.com
Guest

Posted: Thu Feb 26, 2009 12:46 pm Post subject: Absence of Evidence

Roger,

 

   

 

   No "dis" is intended, your "egghead" analysis has one flawed statement - "the absence of the cause is even less likely to produce the signs."  If there is no cause, there is no negative result and NO evidence, 'cause nothing will happen without a cause. Right?

 

 Does this apply to something pertinent?  If so, what is your point?

 

 Jay Bannister

 

 

 

 --

ihab.awad(at)gmail.com
Guest

Posted: Thu Feb 26, 2009 4:41 pm Post subject: Absence of Evidence

On Thu, Feb 26, 2009 at 12:01 PM, roger lambert <n601ap(at)gmail.com> wrote:

 	  Quote: 	
		   In probability theory, absence of evidence is always evidence of absence.


	


You are right, and I stand duly corrected. Thank you. Let me amend my ways:



The fact that the Yuba City report states:



  "no oscillatory loading of the control surfaces was apparent"



counts as evidence against flutter, but should not rule it out;

furthermore, given the paucity of other hypotheses and the various

reasons to continue to suspect flutter (including actual occurence of

it in the fleet), we should continue to pursue this avenue in addition

to others.



Does this work better?



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Fri Feb 27, 2009 5:49 am Post subject: Re: Absence of Evidence

 	  ihab.awad(at)gmail.com wrote: 	
		  On Thu, Feb 26, 2009 at 12:01 PM, roger lambert <n601ap> wrote:

 	  Quote: 	
		   In?probability theory, absence of evidence is always evidence of absence.



	


You are right, and I stand duly corrected. Thank you. Let me amend my ways:



The fact that the Yuba City report states:



  "no oscillatory loading of the control surfaces was apparent"



counts as evidence against flutter, but should not rule it out;

furthermore, given the paucity of other hypotheses and the various

reasons to continue to suspect flutter (including actual occurence of

it in the fleet), we should continue to pursue this avenue in addition

to others.



Does this work better?



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA 	




There is no way to rule out flutter by your standards, since by this logic the absence of flutter raises the possibility that flutter occurred.

ihab.awad(at)gmail.com
Guest

Posted: Fri Feb 27, 2009 7:47 am Post subject: Absence of Evidence

On Fri, Feb 27, 2009 at 1:49 PM, steveadams <dr_steve_adams(at)yahoo.com> wrote:

 	  Quote: 	
		   There is no way to rule out flutter by your standards, since by this logic the absence

 of flutter raises the possibility that flutter occurred.


	


No: I think one *can* reasonably rule out flutter, but this requires

some further testing that I hope gets conducted to put everyone's mind

at ease.



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

ihab.awad(at)gmail.com
Guest

Posted: Fri Feb 27, 2009 7:51 am Post subject: Absence of Evidence

On Fri, Feb 27, 2009 at 3:46 PM,  <ihab.awad(at)gmail.com> wrote:

 	  Quote: 	
		   No: I think one *can* reasonably rule out flutter, but this requires

 some further testing that I hope gets conducted to put everyone's mind

 at ease.


	


And maybe I should correct myself further in that I'm making an

unstated assumption: Even in the case that the Yuba City accident is

not flutter related (in which case it's certainly *weird*), flutter

remains enough of a wildcard that further testing may be in order.



But really I should also say: I'm not a Zenith builder and I have

expressed far more opinions here than I should. Please carry on as you

folks see fit. Thank you for listening. 



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

notsew_evets(at)frontiern
Guest

Posted: Fri Feb 27, 2009 8:11 am Post subject: Absence of Evidence

I honestly dont think anyone is listening.  We have hashed this out long 

before ...

The only AD I ve ever seen on an Experimental was from Zenith.  It relates 

to control cable tension.

---

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Feb 27, 2009 8:51 am Post subject: Absence of Evidence

It wasn't an AD, ADs are strictly US FAA documents. It was a Service  

Bulletin directed at European aircraft. The Zodiac is not the only UL  

aircraft in Europe that has had Service Bulletins issued for it.



In the US, ADs are only issued for type certificated aircraft and  

compliance is mandatory. No such document exists in the US for  

aircraft with experimental certificates. For those aircraft,  

compliance with service bulletins is voluntary. In Europe the rules  

are very different.

 	  Quote: 	
		  

 

 >



 I honestly dont think anyone is listening.  We have hashed this out  

 long before ...

 The only AD I ve ever seen on an Experimental was from Zenith.  It  

 relates to control cable tension.


	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

ggower_99(at)yahoo.com
Guest

Posted: Fri Feb 27, 2009 9:48 am Post subject: Absence of Evidence

This is funny!!!

  

 This is like a "paparatssi"  notice:   

 In an interview with "John Doe" the famous actor, the Paparatssi (P) asked him:  

 Do you think "Pretty Blonde", the singer is attractive?  

 He answers: Yes, she is.  

 Then the P asks: Do you know shes married?  

 JD answers: Yes,  

 P then asks:  Will you date her even married?  

 JD answers:  No, I dont date married women.  

  

 That night In the TV (or the Zenith list:-) the notice is like this:

  

 We found "John Doe, the famous actor running to catch his airplane to Hollywood, but he had the chance to tell us that HE IS IN LOVE with "Pretty Blonde" the singer, He also told us in this exclusive interview that HE WIIL NOT date her until she gets her divorce,  but we will be checking out, He told us also he will not date married women, BUT MAYBE he will date her any week end from now...  Me cant discard any possibility...

  

 Just change "601XL" for the artists, and "flutter" with divorce and dating    .-)

  

 Do not archive...

  

 Saludos

 Gary Gower.

  

 



--- On Fri, 2/27/09, ihab.awad(at)gmail.com <ihab.awad(at)gmail.com> wrote:



  	  Quote: 	
		  From: ihab.awad(at)gmail.com <ihab.awad(at)gmail.com>

Subject: Re: Re: Absence of Evidence

To: zenith-list(at)matronics.com

Date: Friday, February 27, 2009, 10:51 AM



 	  Quote: 	
		  --> Zenith-List message posted by: ihab.awad(at)gmail.com



On Fri, Feb 27, 2009 at 3:46 PM,  <ihab.awad(at)gmail.com> wrote:

 	  Quote: 	
		   No: I think one *can* reasonably rule out flutter, but this requires

 some further testing that I hope gets conducted to put everyone's mind

 at ease.


	


And maybe I should correct myself further in that I'm making an

unstated assumption: Even in the case that the Yuba City accident is

not flutter related (in which case it's certainly *weird*), flutter

remains enough of a wildcard that further testing may be in order.



But really I should also say: I'm not a Zenith builder and I have

expressed far more opinions here than I should. Please carry on as you

folks see fit. Thank you for listening. 



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA



	
	


           [quote][b]

jaybannist(at)cs.com
Guest

Posted: Fri Feb 27, 2009 10:00 am Post subject: Absence of Evidence

Gary,

 

 Very astute !

 

 I see this "absence of evidence" argument as a circular argument that actually gets one nowhere.  It just winds up back in the same place every time - nowhere; proving nothing in the journey..  

 

 Jay Bannister

 Do not archive

 

   

 

   

 

 --

ihab.awad(at)gmail.com
Guest

Posted: Fri Feb 27, 2009 11:00 am Post subject: Absence of Evidence

Gary & folks,



On Fri, Feb 27, 2009 at 9:47 AM, Gary Gower <ggower_99(at)yahoo.com> wrote:

 	  Quote: 	
		   This is funny!!!


	


Please don't try to make fun of me or anyone; this doesn't help the discussion.



As far as my reasoning goes, here it is. When an accident is

precipitated by aeroelasticity, is it possible for perceptible

yielding to only occur on the last cycle so that the yield pattern

only shows the final static failure? The NTSB report did not connect

these dots, leading me to believe that the evidence is not conclusive

either way.



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Fri Feb 27, 2009 12:03 pm Post subject: Re: Absence of Evidence

 	  ihab.awad(at)gmail.com wrote: 	
		  

Please don't try to make fun of me or anyone; this doesn't help the discussion.



As far as my reasoning goes, here it is. When an accident is

precipitated by aeroelasticity, is it possible for perceptible

yielding to only occur on the last cycle so that the yield pattern

only shows the final static failure? The NTSB report did not connect

these dots, leading me to believe that the evidence is not conclusive

either way.



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA 	




Do you have some information that we don't have? I ask because you seem to be assuming that the FAA missed something. Unless you have some evidence that this is the case your position as stated above is pure conjecture.

_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

ihab.awad(at)gmail.com
Guest

Posted: Fri Feb 27, 2009 12:17 pm Post subject: Absence of Evidence

Hi Gig,



On Fri, Feb 27, 2009 at 12:03 PM, Gig Giacona <wrgiacona(at)gmail.com> wrote:

 	  Quote: 	
		   Do you have some information that we don't have?


	


I wish I did and that this information could prevent accidents, but I don't.



 	  Quote: 	
		   I ask because you seem to be assuming that the FAA missed

 something.


	


Not "missed", no. It just seems like they are hedging, and the hedge

stands to reason. There were two options they could have taken:



a. "There was no evidence of oscillatory loading, which leads us to

rule out flutter."



b. "There was no evidence of oscillatory loading."



They chose (b). Had they applied their considerable combined expertise

to say (a), it could have cleared a lot of questions. Unfortunately,

they did not, from which I have to wonder that maybe, based on this

expertise, lack of evidence of oscillatory loading is not, after all,

enough to rule out flutter.



In my mind, failure due to flutter with yield in only one direction is

at least plausible.



 	  Quote: 	
		   Unless you have some evidence that this is the case your position as

 stated above is pure conjecture.


	


Yes, it *is* conjecture. Again, I have no information you don't -- and

certainly no answers.



Over on the ZBAG group, there is currently a push to do some more

testing and analysis that could help everyone rule flutter in or out.

I'm just saying that this effort is good work that remains -- and

needs -- to be done.



Hope this clarifies. Regards,



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Fri Feb 27, 2009 1:16 pm Post subject: Re: Absence of Evidence

 	  ihab.awad(at)gmail.com wrote: 	
		   There were two options they could have taken:



a. "There was no evidence of oscillatory loading, which leads us to

rule out flutter."



b. "There was no evidence of oscillatory loading." 	




I think I've found the problem. You don't speak Governmenteese.



Please find me a single FAA/NTSB report with the phrase "...which leads us to rule out..."



The problem is you can't prove a negative.

_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

ihab.awad(at)gmail.com
Guest

Posted: Fri Feb 27, 2009 1:42 pm Post subject: Absence of Evidence

On Fri, Feb 27, 2009 at 1:16 PM, Gig Giacona <wrgiacona(at)gmail.com> wrote:

 	  Quote: 	
		   I think I've found the problem. You don't speak Governmenteese.

 The problem is you can't prove a negative.


	


That may indeed be a fair analysis.



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Sat Feb 28, 2009 2:23 pm Post subject: Absence of Evidence

and elvis is alive in Greenland, married to the alien that landed at aera 51.  put it to bed.

do not archive    Juan



--

JAPhillipsGA(at)aol.com
Guest

Posted: Sat Feb 28, 2009 4:50 pm Post subject: Absence of Evidence

Juan, you going to SnF this year? It'll be good to see you  again, hear your stories and drink your beer.  Best regards, Bill of  Georgia

  

  In a message dated 2/28/2009 5:24:41 P.M. Eastern Standard Time,  amyvega2005(at)earthlink.net writes:

 [quote]-->    Zenith-List message posted by: Juan Vega    <amyvega2005(at)earthlink.net>



and elvis is alive in Greenland,    married to the alien that landed at aera 51.  put it to bed.

do not    archive    Juan



--

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Sun Mar 01, 2009 1:35 pm Post subject: Absence of Evidence

i shall be there my Brotha.



Juan



--

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Sun Mar 01, 2009 1:49 pm Post subject: Absence of Evidence

You forgot to mention that the NTSB and the FAA ran computer models  deconstructing the plane various times and building it by CAD CAM design various times,  and found that the plane is designed well, and has no bad tendencies and mostly the models don't show any hidden or bad design characteristics.



What this means is in the Absense of speculation and mental masturbation, which you guys keep doing to the point of bad chaffage,(makes for bigger calluses)  there was clear evidence that the pilots or the builders, notice the builders, not the design,  were the culprit.   BUild it well, take care of it correctly, fly it well makes for a safe plane.   

YOu guys that are jerking your selves have taken a good name of a well designed plane, and dragged it through the mud. from  those of us that built one and now have to defend its design to others becuase of a bunch of arm chair quarter backs that refuse to look at clear evidence of crappy piloting and poor maintenace,  I say kiss my  %$#!(at).  You get the picture.



do not archive



--

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