# Binomial distribution question-S1

#1
Could someone please explain how you do this question.Please show working out.

Given that D~B(12,0.7) calculate

A) P((D<4)
B)The smallest value of d such that P(D>d)<0.9

i can do A but thought I'd include it if the answer is at all involved in B.
0
8 years ago
#2
(Original post by Anonymous 14)
Could someone please explain how you do this question.Please show working out.

Given that D~B(12,0.7) calculate

A) P((D<4)
B)The smallest value of d such that P(D>d)<0.9

i can do A but thought I'd include it if the answer is at all involved in B.
Since P(D>d) = 1-P(D <= d)

You're looking for the smallest d, such that 1-P(D<=d) < 0.9

Or rearranging.

0.1 < P(D<=d)

The result of part b) tells you that d > 3, so you need to try 4, 5, .... for the cumulative probability to get a value > 0.1
0
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