Bunuel wrote:
1. The probability that a convenience store has cans of iced tea in stock is 50%. If James stops by 3 convenience stores on his way to work, what is the probability that he will be able to buy a can of iced tea?
James will be able to buy a can of iced tea if at least one of the shops has it and the probability that at least one of the shops has an iced tea is P=1-(none of the shops has an iced tea)=1-P(NNN)=1-1/2^3=7/8.
2. The probability that a convenience store has no iced tea is 50%. If James stops by 3 convenience stores on his way to work, what is the probability that at least one of the stores will not have a can of iced tea?
The probability that at least one of the stores will not have a can of iced tea is 1-(all shops have an iced tea)=1-P(YYY)=1-1/2^2=7/8. Notice that we have the same answer as above. That's because the probability distribution is symmetrical for this question thus the probability that at least one of the stores will NOT have a can of iced tea = the probability that at least one of the stores will have a can of iced tea
3. The probability that a convenience store has cans of iced tea in stock is 50%. If James stops by 3 convenience stores on his way to work, what is the probability that he will not be able to buy a can of iced tea?
James won't be able to buy a can of iced tea if none of the shops has it: P(NNN)=1/2^3=1/8.
Hope it's clear.
Hi Bunuel,
WRT Q2.
P(atleast one does not have)= P(one does not have) + P( two don't have) + P(all 3 don't have)
= P(one does not have)*P(2 have) +
P (2 don't have)*P(one has) +
P(all 3 don't have)
= 1/2*1/2*1/2 + 1/4*1/2 + 1/8
= 3/8
Why is it giving me a wrong answer?I know I am missing something.
Can someone please explain?
Infact Is my methos wrong, coz i am trying to solve Qs by this method. I understood the 1-p methos as well.
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