# math- statistics

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If the probability of a swan drowning is 0.23, find the probability of exactly 4 out of the 7 swans drowning.

I think that the answer is:
(0.23)(0.23)(.00003404)= .000001801

is the right?

• math- statistics -

p of drowning = .23
1-p = prob of not drowning = .77

In general the probability of k hits in n trials is
C(n,k) p^k (1-p)^(n-k)
(binomial random variable )
so here we want
C(7,4)* .23^4 * .77^3

C(7,4) from Pascal's triangle of combination formula = 35
so
35 * .23^4 * .77^3 = .0447

• math- statistics -

thank you so much!!!

• math- statistics -

If the probability of a lame leaping lord is 0.24

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