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Binomial Probability Issue!?
During winter it rains on average 18 out of 30 days. Five winter days are selected at random. Find, correct to four decimal places, the probabiity that:
a) the first two days chosen will be fine and the remainder wet,
b) more rainy days than fine days have been chosen
@ Bail Out
thanks for the attempt, that's basically what I have been doing the entire time. According to the back of the book, the answer to a) is 0.0124 and b) 0.7102
1 Answer
- Bail OutLv 61 decade agoFavorite Answer
Let X days among the selected 5 days be wet.
Then, X ~ B(n=5, p=18/30=0.6)
p(x) = 5Cx*0.6^x*0.4^(5-x), x=0,1,2,3,4,5
a) P[the first two days chosen will be fine and the remainder wet]
= 12/30*12/30*18/30*18/30*18/30
b) P[more rainy days than fine days have been chosen]
= P[X > 5-X]
= p(3) + p(4) + p(5)
Hope this helps