Statistics - Binomial Distribution Help Needed

Hi i'm doing S1 and there is one thing that i don't seem to get.
If i'm trying to find P(6<x<12) for example where B(50,0.15)

I know i need to find the probability that x<12 but i don't understand why you don't do x>6.
In the answers for AQA S1 June 2010 it says i must use 1-p(x less than or equal to 6) and i don't know why.

If someone could tell me how to do this type of question and why i'm getting it wrong it would help a lot.
Thanks

Reply 1

TeeEm

19

Original post by JamestheYorks

Hi i'm doing S1 and there is one thing that i don't seem to get.
If i'm trying to find P(6<x<12) for example where B(50,0.15)

I know i need to find the probability that x<12 but i don't understand why you don't do x>6.
In the answers for AQA S1 June 2010 it says i must use 1-p(x less than or equal to 6) and i don't know why.

If someone could tell me how to do this type of question and why i'm getting it wrong it would help a lot.
Thanks