So you are given the probability of an event happening. And you are required to find out the probability that you need more than n=8 trials for the event to occur.
so to recap
p = 0.15
n=8
Check out a book on distributions. the distribution you want is a B------- distribution.
and remember that P(A) = 1-P(A")
where A is an event. and A" means the event does not occur.
let n be the number of trials before a Rh negative person is found.
so you want P(n>8)
P(n>8) = 1 - P(n<=7)
hmmm...think i've hinted too much... but there you go... shooo...
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