View Full Version : How do I explain risk?

10th Sep 2011, 15:01
Please help me:

1. I read from a local newspaper that a NASA Upper Atmosphere Research Satellite is about to re-enter the atmosphere (will drop down, if you will) and that, freely translated; "according to NASA calculations, the probability that the pieces hit someone is less than 3 per mil".

I dug up this from NASA web site for my own education: http://www.nasa.gov/pdf/585584main_UARS_Status.pdf

2. A person I know needs medication after his surgery, and the package leaflet, among many things, explains that rare side effects of this drug are, among some others, allergic skin reactions, hives, fainting, and feeling unwell. On the other hand, rare (less common than "uncommon" and more common than "frequency is not known") side effect is something that happens to one user per 1,000 to 10,000 users (1 per mil - 0.1 per mil) It does not matter to know which drug this is, but these are real numbers.

Your task: Tell me how to explain to this person that the falling of the four ton satellite is not dangerous to him. Lay terms, please - be less serious, serious, or dead serious - as you please.


10th Sep 2011, 15:11
Tell him there's a higher chance of being hit by lightning whilst sitting on the toilet receiving oral sex from <insert female/male of your choice here> than there is of being hit by any of the pieces of the satellite that are left after going through re-entry.

10th Sep 2011, 15:26
Hellsbrink, thank you.

This person has had oral sex in an aircraft toilet, and been in a 747 hit by a lightning on approach to Schiphol (separate occasions, granted), so he is no stranger to risk (hey guys, I am not making this up).

But, Hellsbrink, how do you get your conclusion from the facts and figures in the case?

10th Sep 2011, 15:36

I've never been hit by a piece of a satellite that has dropped from orbit and I've never been hit by lightning whilst receiving oral sex whilst sitting on a toilet. And since there has never been a piece of a satellite land nearby (within miles) of me whilst receiving oral sex when sitting on the toilet, whereas there has been lightning in the vicinity of the building in which a toilet where I received oral sex whilst sitting on it was housed, it's a fair assumption to say that the chances of being hit by the space debris is lower.

10th Sep 2011, 15:39
Would he expect to win the lottery if he bought one ticket? If he does, he's a goner.


Mad (Flt) Scientist
10th Sep 2011, 15:50
Chance of a human casualty - 1 per 3200 according to the link (which sounds conservative to me, but taken at face value)

Number of human, 6 billion or so.

Chance that you will be the human casualty 1 in 6 billion times 1 in 3200 = 1 in a huge number (2 trillion or so)

Basically, there is a moderate risk that any human will be injured.
There's an almost impossible risk that a specific human will be hit.

The lottery example is a good one. There's a one in 100-1000 chance that a human will win a rollover/special jackpot, depending on the lottery. But if 10 million humans are in the lottery, its a one in (100-1000)times(10 million) chance that a specific person will win. So don't buy a ticket based on 1 in 100 chance that SOMEONE will win - it's the chance that you win that counts for you.

10th Sep 2011, 16:14
<insert female/male of your choice here>

Mischa Barton.

10th Sep 2011, 16:24
There's a chance out of two he will be hit ; he will be... or not.
He should trust the NASA specialists, enjoy life until every bit is on the ground, instead of worrying about that. There's nothing much he can do anyway...

There's also a chance out of two he dies from something else before a debris hits him.

If he's hit, there's a chance out of two he will be wounded, not dead... and suffer lifelong aftermaths from this highly unlikely encounter.

10th Sep 2011, 16:31
Well, maybe we should throw in a zero-assumption: If you don' take those pills, the risk of those side effects from those pills is zero.

The same goes for the debris: If you don't stand/sit/lay under the trajectory of that satellite, you won't be harmed by it's falling, for sure.

I am still adrift. Does NASA's calculation make much sense (I don't want even to think about the drug calculation/estimate)? If M(F)S makes any sense, which I believe is the case, NASA's may not be that conservative regarding the people under the orbit/trajectory.

Still need to explain this to the guy…. :hmm:.

Edit: Maybe I explain all this to him with exposure. As he (assume this) is outside the area under orbits, let alone the intended drop trajectory, he should be free of fear on that front. On the other hand, if he continues taking the pills and then faints (see post #1), he can always sue the manufacturer. Right?

Krystal n chips
10th Sep 2011, 16:49
So how come, risk wise, so many unfortunate people seem to be either sitting in a car or passing by / sitting at home when a tree decides after numerous years, to fall over in a decent gale then ?.....

tony draper
10th Sep 2011, 16:54
Seems to me if people can walk round Libya and not get hit by a falling bullet there's not much chance of a bit of satellite scragging you.

10th Sep 2011, 17:04
What are the odds of winning the lottery? Pretty high. But people win it regularly. I managed five numbers once which is the equivalent of the satellite landing in my back garden.

The odds of it happening are irrelevant to the person who gets flattened by a piece. The thing to bear in mind is that we all have the same chance of being hit by the satellite or of winning the lottery as the actual person unlucky or lucky enough to find themselves in that position.

In my own case I suspect that if I found myself ticking off the final number on the Lotto slip the sky would be lit by a strange light followed by a whoosh that I would never hear. :ooh:

10th Sep 2011, 17:26
Best way to convince him is to suggest that he goes to an insurance company and asks for a quotation to insure him against the event. I know that insurance companies are rapidly becoming the new pariahs of society but they should quote a really low premium.

A friend of mine insured himself against his staff winning a substantial prize in the lottery and then leaving him with no staff. The annual premium was about the same as each person's weekly contribution.

10th Sep 2011, 17:46
Pulse1, good!

I was once in my previous life part of a company who made some risk assessment exercises. I was not part of the assessment but was there when the result was presented. One of the issues (according to rumours) was causing a lot of concern and discussion in the team (I wonder where the mathematicians were at the time) was that the company had a production plant about 4 km from the threshold of a little used runway, about 2 km from the extended centerline, next to a relatively busy commercial airport (by any standards). So a major risk identified was a complete devastation of the 2 acre production hall and the loss of life, property, and earnings, because of a crash.

I asked how much the company uses for all the insurance premiums it is paying to the insurers for all risks. Then I asked how much they thought the would need to pay more to get a full coverage against an MD-11 ramming the plant full of fuel.

They could not come up with anything except that it must be very much. My own estimate was something along the lines that 5 to 15 dollars self insurance (money in bank each year to cover the risk) would be appropriate. They didn't laugh at me (they wouldn't dare) but they did not take me seriously, either. Would you have?

10th Sep 2011, 18:17

10th Sep 2011, 20:01
Give him the facts, and let him make his own mind up.

If he doesn't understand the bigger picture, use something pictorial, like a grid diagram.