ct3 text book question number 11.7

lease tell where i am making a mistake

for p(x>=7)=.025
{(8C7)p^7(1-p)1}+{(8C8)p^8(1-p)^0}=0.025
p value comes to around 0.458 but ans is 0.4735


again for p(x<=7)=.025
1-P(x>=7)
1-{p(x=7)+p(x=8)}=.025
p(x=7)+p(x=8)=.975
expanding
8P^7 -7P^8=.975
p comes to around 0.9711

please clarify

 

Here in calculating the lower end of the interval , i think you are making some calculation mistake , i solved it and got p=0.473.. . As far as upper end of interval is concerned
P(x<=7)=1-P(x>7) , you have considered p(x<=7)=1-p(x>=7)

 

Dear Divyam

thanks for correcting me, but i have doubts regarding upper and lower end. since we are doing normalisation of Binomial , so lower end of the normal curve should be x<=7 and upper end is x>=8

but we are taking p(x<=7) as upper end

please clarify

regards

suresh sharma

 

We are not using normal approximation here as 'n' is not large enough and also the question states that we have to solve it using binominal distribution .In this sum lower end can be obtained by solving p(x>=7)=0.025 and upper end is obtained by solving p(x<=7)=0.025 . The proof of this complex relation is on page 13,14,15 of chapter 11

 

thanks

 

Thanks Divyam