Mailing List lml@lancaironline.net Message #36968
From: <Sky2high@aol.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Safety statistics and other mythology
Date: Tue, 01 Aug 2006 14:31:48 -0400
To: <lml>
Hmmmmm........  A new soap opera: As the Thread Turns
 
Brent's view of statistics (the plural of statistic) is from an engineer's perspective.  Lorn didn't go far enough.  Terrence used 20 year old information and threw in some strongly held personal views.  Others have sought to explain certain sub-sets of the universe of air accidents by comparing dissimilar groupings.
 
If you have gotten to this paragraph perhaps you will continue.  Note that statistic is defined in an online dictionary as follows:
 
  1. A numerical datum.
  2. A numerical value, such as standard deviation or mean, that characterizes the sample or population from which it was derived.
While it took me eleven years to get a simple BS (yes, that is the correct expression) in Math, the middle years (1960's) were devoted to computers, with some time spent writing programs on vacuum tube and transistor computers to turn vast quantities of #1 into a wide variety of #2 (yes, #2).  Interestingly, statistics alone should not be our real concern.
 
LML contributors so far have tried to perform the function of the insurance companies (Lorn, jump in any time).  To wit, assigning a probability to an event which causes the death of an aircraft occupant when the reported statistic is grossly limited to gigantic subpopulations such as GA and Commercial Aviation.  There are mathematical methods to determine the probability of heads on the next coin toss and even more complex event outcomes based on intervening conditions.  I wonder if this is where Brent meant a lower branch of math?  After all, a form of this math is applied to "theoretical" physics (Lorn, hit'm with the random nature of #1 above) to help explain various natural wonderments.  I gave up on studying probability theory when the conditions got too complex.
 
The insurance companies have not given up on conditional probabilities (this must be what they call actuarial science).  Their motive is straight forward - What premium should be charged to some population so that when certain covered events occur, less is paid out than taken in.  When a person obtains insurance coverage for an air event that leads to death and destruction (crash among others), the company tries to limit the population so that their motive is met.  For example, a transitionally trained pilot with a minimum number of hours in similar type that is retrained each year and is young enough without too many DUI's can get such protection while someone falling outside that population is eliminated or must fit into a population where higher premiums are paid.
 
If you are still with this piece, please note that the probability of your immediate demise is far more complex than using general aviation population statistics combined with the wing design of the airplane flown.  There are so many ways to go.  For example, in the greater population, the category "home accidents" is a killer, but since you built your plane and still have all your fingers and toes the chances are you won't perish that way (Hmmmm, an opinion, not a statistic).
 
Now, to get personal I must describe the subpopulation I exist in - I drive a performance car without side airbags and use speed to get out of dicey situations, I frequently travel expressways in excess of 75 mph (65 Kts) on a motorcycle, I am overweight, I eat and drink almost anything in moderation, I operate dangerous home garden manicure equipment, I fly a hi performance airplane that I built in my garage and I don't challenge Mother Nature too much. I also avoid flying commercial airlines, especially those that keep turning up with drunk pilots or are based in certain exotic locations.  Oh, I clean my own guns and I don't allow terrorists to board my aircraft either.  
 
So, is the probability less or greater that I will perish in my Lancair or of that because I am a member of the GA population?  I don't care because I am a special case.  Besides the advanced institutional care I receive and ever higher med doses, I respect the flight characteristics of my airplane.  And that alone apparently puts me in a different population from those that think they are still flying a Cessna whilst directing their hi-perf experimental craft about the sky.
 
Risk analysis is different for the individual or the insurance company because of very different interests.  Statistics are useful to the latter and not particularly useful to the former.
 
Scott Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

Abnegate Exigencies!
 
 
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