GARP 2011 Exam paper. part 1 / exam 1

[alexjr]

Sorry if my question sounds dumb, but I am still don't get Q1 (distribution between 55 and 65) question (i.e. rational behind getting 0.9332-0.6915=0.2417). Anyone can explain it to me in lame terms? thanks

 

[alexjr]

similar question in 2010 exam paper par1 question 17:
assume that a random variable follows a normal distribution with a mean of 100 and STD of 17,5/. What is the probability that this random variable is between 82.5 and 135?

I understand that 82.5=100-17,5 (-1 STD) and 135=100+17,5*2 (+2STD), which gives us

-1 STD<x<+2STD
how did we get following numbers (1-0.0228)-0.1587=0.8185

thanks

 

[[email protected]]

Hi,

numbers are from cum z table (z1=0.8413 & z2=0.9772)