Hi,
The tables ( pg 160 and 161 of the Formulae and Tables book) give values of probabilities of x greater than Z,i.e P(Z<x). Here are certain formulas that may help you:-
1) if P(Z< -x)= P(Z>x)=1-P(Z<x)
2) if P(Z> -x)=P(Z<x).
In your example we have to find P(Z>1.165). So using the first formula it becomes-
1-P(Z<1.165).
The tables provide probabilities up to 3 significant figures,so we need to interpolate the probabilities. Now, we know that 1.165 lies between 1.16 and 1.17. the formula for interpolation is-
P(Z<1.16)+0.5{P(Z<1.17) - P(Z<1.16)}
(The 0.5 above is from the third significant figure. Suppose if it was 1.1669 instead of 1.165, then we need to put 0.69.)
From the tables we get:-
=0.87698+0.5{0.879-0.87698}
=0.87799
Therefore , 1-P(Z<1.165)=1-0.87799=0.12201
I really hope this helped!
Kid regards,
Sanjay.
Last edited by a moderator: Mar 10, 2015