Stats question (Paper 6)

[AayushR]

In M/J 09, 1.(i), how is the value of z found?

I need to know asap. Thanks.

http://www.xtremepapers.me/CIE/Internat ... 9_qp_6.pdf

 

[Amna]

225 out of 900 have more than 1002 ml therefore P(X>1002)= 0.25
==> P(X<1002)= 0.75
z<(1002-mean)/sd
from the table of normal distribution, in the critical values table, we get P= 0.75 when z=0.674
so 0.674(8) = 1002 - mean
mean = 996.608 or 997

 

[sassmos]

wat about (ii)??