The likelihood that it will rain in Wilmington on Monday is 60%. the chance that it will rain in Burgaw on Monday is 70%. However, if it rains in Burgaw on Monday, then there is a 80% chance that it will also rain in Wilmington on that day. What is the probability that it will rain in a least one of the above two cities?
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Likelihood it will rain
- Thread starter lcf4712e
- Start date
J
JeffM
Guest
lcf4712e said:The likelihood that it will rain in Wilmington on Monday is 60%. the chance that it will rain in Burgaw on Monday is 70%. However, if it rains in Burgaw on Monday, then there is a 80% chance that it will also rain in Wilmington on that day. What is the probability that it will rain in a least one of the above two cities?
If A and B are two different events with probabilities of P(A) and P(B) respectively, THERE IS A GENERAL FORMULA for the probability A or B.
Do you know that formula?
THERE IS ALSO A GENERAL FORMULA for the probability of A and B.
Do you know that formula?
Do you see a way to apply those formulas to the problem at hand?
J
JeffM
Guest
lcf4712e said:I think the formula would be P (A u B) = P(A) + P(B) - P (A intersect B).
Yes. That is one of the fundamental formulas of probability theory.
This is new to me and I have a problem deciding what numbers go where.
In the formula above, A and B are just LABELS for what statisticians call "events." You can substitute in whatever event you want. So
Let A = Rain in Wilmington
Then P(A) = 60% = 0.6.
I have been out of school for over 30 yrs.
Not a problem. It has been longer for me.
OK Now what is B and P(B)?
What does (A and B) mean?
Do you understand WHY P(A or B) = P(A) + P(B) - P(A and B)? Memorization is much easier when you understand why as well as what.
To calculate P(A and B), we need another formula. Do you know a formula for that?