Plane crash
 

Im sorry, Im confused. Suppose the risk of any plane crashing is 1/5. You know that Joe will take 7 flights next year. What is the probability that Joe will die next year?

Re: Plane crash
 

[ QUOTE ]
Im sorry, Im confused. Suppose the risk of any plane crashing is 1/5. You know that Joe will take 7 flights next year. What is the probability that Joe will die next year?

[/ QUOTE ]

There isn't even close to enough information there. Do you mean the chance that any particular flight crashes is 20%, or that a plane crashes is 20%? How likely is a plane crash to be fatal? What other causes of death are there for Joe?

That said, let's assume that there is a 1/5 chance that a flight crashes, and we want to calculate the likelihood that at least one of the 7 flights that Joe is on will crash.
It's easier to calculate the probability that none of them crashes, and subtract from 1.
1-(4/5)^7=61777/78125

So we come up with a plane crash about 3/4 of the time.