# What is p (prob. of sucess)?

#### haswell

Regarding question 9e (shown in the attached picture), I'm aware that the question needs the binomial distribution with n = 36 and I know that the required is the probability of X (No. of Oranges) greater than 18. My main issue is what is p (the probability of success which is needed as part of the binomial distribution of X~Binom(36,p)?
I've no clue about 9f either.
Thanks!

#### Attachments

• 573.2 KB Views: 10

#### mathman

Forum Staff
It looks like p=.65, since the grocer is looking for oranges with weight greater than the 35 percentile.

#### romsek

Math Team
It looks like p=.65, since the grocer is looking for oranges with weight greater than the 35 percentile.
I think you have to use that as the $p$ parameter for a binomial distribution with $N=36$

$$\displaystyle P[\text{grocer buys more than half a box of 36}] = 1 - \sum \limits_{k=0}^{18} \dbinom{36}{k} (0.65)^k (0.35)^{36-k} = 0.95428$$