Question

what is the probability that at least 2 will survive if expectancy for 3 people are 0.1,0.2,0.3

Answer 1

1st we need to clear up what those probabilities represent. You said "expectancy".Are those their probabilities of dying or living?

Answer 2

living

Answer 3

PR(AdiesBlivesClives) + Pr(AlivesBdiesClives) + Pr(AlivesBlivesCdies + Pr(all live)
0.9*0.2*0.3 + 0.1*0.8*0.3 + 0.1*0.2*0.7 + 0.1*0.2*0.3

Answer 4

For each person, the probability they die is 1 - Pr(live)
1-0.1=0.9
1-0.2=0.8
1-0.3=0.7

Answer 5

okay so we use the compliment correct?

Answer 6

Yes...for the probability of dying.

Answer 7

i got 0.098 for the total. is that the answer or do i have to do something else?

Answer 8

That's what I get, too

Answer 9

These people must have some terrible disease to have such small chances of living!

Answer 10

i know right haha these are just the numbers my teacher gave me

Answer 11

so how would i find the probability that only 2 will survive

Answer 12

Same way...just leave off that last 0.1*0.2*0.3...which was the prob that all 3 live.

Answer 13

alright thank you!

Answer 14

No problem.

Answer 15

A little secret. I actually used to work for a life insurance where we actually had to consider the probabilities of people dying when setting life insurance rates. So these types of questions are VERY familiar to me

Answer 16

did you get 0.092?

Answer 17

oh really?! hopefully you werent getting numbers like these were you?

Answer 18

oops! yes you are correct.

Answer 19

oh alright i just rechecked it all i was confused haha