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article imageProbability of dying from H1N1

By W. Christopher Epler     May 2, 2009 in Science
Swine Flu, or H1N1, may be frightening us too much. Let's examine the probabilities and compare them to dying of other catastrophe's.
Let's begin with being struck by lightening. In the US an average of 80 people are killed by lightening each year. If we assumed everyone is equally likely to be killed by lightening, then this probability would be approximately 80 divided by 250 million, or a probability of 0.000032 percent.
However, this writer used to do runs around the law school of a university and someone actually died from being struck by lightening during that period, so this tiny probability doesn't mean its OK to do runs in the rain, especially when you see lightening flashes here and there.
Oddly, the probability of dying from a plane crash has increased. In 2001, 1,118 people died out of 1,238 people on board, which is a fatality rate of 90% However, in the previous decade, only 72 percent of people died in crashes. This, by the way, is an example of a conditional probability, not a probability like dying by being struck by lightening. To say it formally, P (you die, given that you are in a plane crash in 2002) = .90.
This is like asking what's the probability that you get a queen on the second draw from a deck, "given" that you got a queen on your first draw. Well, that depends on whether you put the first queen back in, doesn't it? If you return the queen after the first draw, then the probability of getting a queen on the second draw will be 4/52, just like the first draw. However if you don't return the queen to the deck after the first draw, the probably of getting a queen on the second draw will be 3/51.
And here's a slight surprise. Experts believe the probability of being killed by an asteroid impact is four times higher than dying of a plane crash. An asteroid smaller than one km across smashing into the Earth at 321 cm per second would cause an explosion greater than 1000 of the most powerful hydrogen bombs ever detonated. What's worrisome about asteroids and comets is that many have trajectories totally unknown to astronomers -- at least not known until they are announced on nighttime news.
You know, after such an announcement, I think I would run in lightening storms to my heart's content.
One of the more mind bending historical probabilities has to do with the Monte Hall TV show, "Let's Make a Deal". The "deal" was that the contestant was faced with three doors, behind one of which was a brand new car, and behind the other two were often goats. However, this show had a clever twist, because after the contestant picked a door, Hall would open one of the unpicked doors, behind which there would be no car, and then the contestant would have a chance to change his/her mind -- with the audience going berserk with advice.
The common sense was that it didn't make any difference, so change or not change, the probability of winning would simply be 1/2. However, this is false and the contestant should always change since (to over simply a tad) if he/she had picked door A and Hall had picked, say, door C, the probability of the car being behind door B was now 2/3. Remember, the probably of it "not" being behind door A was 2/3, and Hall's choice of door C didn't change that fact. It helps to factor in the fact that Hall would never pick a door with the car behind it.
OK, so what's the probability of dying from so-called Swine Flu, even though the W.H.O. has compassionately changed its name to H1N1 to protect pigs from being slaughtered since they are innocents in this disease? So pig out at your leisure.
Well, once again we're back to conditional probably, since the probability of dying of swine flu is much less than the probability of dying from swine flu "given" that you have become infected with H1N1, and the data is very slim to date on either.
However, to use Canada as a test case, up to a few days ago there had been six cases of this flu. The data suggests the probably of dying from H1N1 if you get it is less than one percent, so if you do the math and shuffle Canada's 33 million people and give six of them swine flu, the probably of a specific "you" dying from it would be about 0.0000000018.
Remember, there are two probabilities here. The first is the probability you get it in the first place, and the second is the probably that you die from it, given that you get it. The probability that you get it and die from it is the product of those two probabilities.
This last example is for those who like a pinch of formality seasoning. The probability that the first and second draws from a deck are both queens (again assuming you don't return the first queen to the deck) is: P (Q1 and Q2) = P (Q1) P (Q2|Q1) = 4/52 * 3/51 = 12/2652 = 0.45 percent. Remember, multiplying numbers less than one can give exceedingly small numbers.
However, my big question is still how did Benjamin Franklin not die when flying his kite in that lightening storm? Talk about low probability luck!
More about Probability, H1n1, Monte hall, Death
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