Binomial help please!

OP

Original post by mqb2766

Half correct. Why not read that section of your notes/book/google/... again.
http://www.a-levelmathstutor.com/stat-binomial-distribution02.php

If you don't understand the starting point, doing the question is a bit pointless.

I understand it however I still don’t get how to solve for p

Reply 7

Original post by pearllx

I understand it however I still don’t get how to solve for p

What have you written down for the two probabilities?

Reply 8

OP

Original post by mqb2766

What have you written down for the two probabilities?

P(X=5) = 56p^5(1-p)^7

P(X=6) = 28p^6(1-p)^7

Reply 9

Original post by pearllx

P(X=5) = 56p^5(1-p)^7

P(X=6) = 28p^6(1-p)^7

The powers of p and (1-p) add up to n (8). The p ones are correct, but not the (1-p).
Also, sometimes it's easier to cancel down the nCr numbers leaving in factorial form, but in this case it makes little difference.

(edited 3 years ago)

Reply 10

OP

Original post by mqb2766

The powers of p and (1-p) add up to n (8). The p ones are correct, but not the (1-p).
Also, sometimes it's easier to cancel down the nCr numbers leaving in factorial form, but in this case it makes little difference.

I thought so too but the formula said n-1 so I assumed the powers would be 7

Reply 11

Original post by pearllx

I thought so too but the formula said n-1 so I assumed the powers would be 7

Just look in your textbook. If you don't have one, get a copy. Many places online ...

Reply 12

OP

Original post by mqb2766

Just look in your textbook. If you don't have one, get a copy. Many places online ...

The website u sent me said the powers should be n-1 so I got confused

Reply 13