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On 1 Nov, 22:46, Chris Reed wrote:
If we ignore the past, however, each day's chance is the same at 0.5. Thus Ray (may he live forever) is able to state that next year his chances will be pretty much the same, if he makes it that far. That's not his claim, though. He seems to be saying that his chance of dying tomorrow is 1 in 80, his chance of dying the day after that is 1 in 80 and so on to 1st November 2008, but that his chance of dying at all during that year is still only 1 in 80. I do hope he'll explain, in case I'm missing something obvious ... Cumulation of probabilities is what the human brain does automatically. Suppose the chance of being killed on a glider flight is 1 in 1,000. The mind (without extensive training) deals with this in a number of ways: The prblem, of course, is that one cannot be killed twice, so it does not make sense to combine (simply) the probabilities of dying on different days. Multiple survival is the aim, and survival probabilities can be combined quite easily. Just recast our statement as "The chance of surviving a glider flight is 999 in 1,000"... 3. At my club we fly 1,000 flights a year between us, so one of us is sure to die flying. There's actually a 63% chance that one of you will have bought the farm by the end of the year. Get a new safety officer! a. In the UK where I fly, gliding fatalities are on average around 2.5 per annum out of 5,000 pilots, so my "statistical" risk is around 1 in 2,000 of dying through gliding each year. Agreed. b. I can do a number of things to reduce my personal risk to less than 1 in 2,000, so I'll try to do those things. Agreed. c. This is, to me, an acceptable level of risk for the pleasure I get from gliding. Agreed. The good thing is that these probabilities are not cumulative. I've been flying for 11 years, so if they were cumulative my "statistical" risk might be down to under 1 in 20. It ain't. Your chance of making it through the next 11 years is still 99.5% I reckon you can improve that to 99.95% by application of non-stupidity! Ian |
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On Nov 1, 7:32 pm, Ian wrote:
On 1 Nov, 22:46, Chris Reed wrote: If we ignore the past, however, each day's chance is the same at 0.5. Thus Ray (may he live forever) is able to state that next year his chances will be pretty much the same, if he makes it that far. That's not his claim, though. He seems to be saying that his chance of dying tomorrow is 1 in 80, his chance of dying the day after that is 1 in 80 and so on to 1st November 2008, but that his chance of dying at all during that year is still only 1 in 80. I do hope he'll explain, in case I'm missing something obvious ... Cumulation of probabilities is what the human brain does automatically. Suppose the chance of being killed on a glider flight is 1 in 1,000. The mind (without extensive training) deals with this in a number of ways: The prblem, of course, is that one cannot be killed twice, so it does not make sense to combine (simply) the probabilities of dying on different days. Multiple survival is the aim, and survival probabilities can be combined quite easily. Just recast our statement as "The chance of surviving a glider flight is 999 in 1,000"... 3. At my club we fly 1,000 flights a year between us, so one of us is sure to die flying. There's actually a 63% chance that one of you will have bought the farm by the end of the year. Get a new safety officer! a. In the UK where I fly, gliding fatalities are on average around 2.5 per annum out of 5,000 pilots, so my "statistical" risk is around 1 in 2,000 of dying through gliding each year. Agreed. b. I can do a number of things to reduce my personal risk to less than 1 in 2,000, so I'll try to do those things. Agreed. I appologise for starting a statistical discussion; there's enough of that at work. The important point is the one made in Chris's post that gliding carries a risk in the range of one to between two and three thousand depending on what denominator is used. Serving in Iraq carries a similar risk, but the population isn't uniform; there's clearly a difference in being in being part of the rear echelon vs patrolling the streets. Our population is similarly stratified in terms of risk. There are also, unfortunately, factors beyond personal control in play. As I've aged, I've noted that I need a bit more distance between myself and the car in front of me. My head needs to swivel to a greater degree to see things in the periphery. These effects can be measured/quantified. Medical events such as stroke or MI have been suggested as the cause of a number of accidents; the ones that killed the student who soloed ahead of me where I learned to fly in SoCal and that of a friend who crashed during the return to Kitty Hawk were likely caused by medical incapacitation. As I age, my risk of such events increases. The important thing, IMHO, is to recognize the risk, decide what you're willing to accept, and, if you choose to go forward, control what you can and hope that what you can't won't kill you. Ray Warshaw 1LK c. This is, to me, an acceptable level of risk for the pleasure I get from gliding. Agreed. The good thing is that these probabilities are not cumulative. I've been flying for 11 years, so if they were cumulative my "statistical" risk might be down to under 1 in 20. It ain't. Your chance of making it through the next 11 years is still 99.5% I reckon you can improve that to 99.95% by application of non-stupidity! Ian |
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On Nov 2, 12:21 pm, 1LK wrote:
Serving in Iraq carries a similar risk, but the population isn't uniform; there's clearly a difference in being in being part of the rear echelon vs patrolling the streets. It is always worth comparing one risk with another, as a sanity check. During the first Gulf War in 1991, it was safer to be a black GI on active service in the Gulf than it was to be a black civilian in Washington DC. In this case "safer" means probability of non-accidental death per 100,000 people. When I first heard that I was sufficiently suspicious that I went down the library (it was just as the web was arriving) and checked the sources myself. The other surprising statistic is the age at which you are most likely to be a homicide victim in the UK. Most people presume 16-24, but actually it is three times more likely to be deliberately killed when you are under 1 year old. And 55% of those homicides are committed by females. (N.B. I used "homicide" very deliberately, not murder) |
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