# Normal Distribution question

• Aug 31st 2011, 12:28 AM
Paymemoney
Normal Distribution question
Hi
Can someone help me on the following questions:
Determine the value of z in the following case: Pr(-z<Z<z)=0.954

I done InvNorm(0.954,0,1) but this is incorrect

Find the quartiles of the standard normal distribution?

P.S
• Aug 31st 2011, 12:46 AM
Re: Normal Distribution question
first find the $\textrm{P}(Z

it will be equal to $\frac{0.954}{2}+0.5=0.977$

so find z according to that value from the data sheet
• Aug 31st 2011, 01:02 AM
Paymemoney
Re: Normal Distribution question
Quote:

first find the $\textrm{P}(Z

it will be equal to $\frac{0.954}{2}+0.5=0.977$

why do you have to plus 0.5 after halving 0.954?
• Aug 31st 2011, 01:17 AM
Re: Normal Distribution question
because normally on datasheets, $\textrm{P}(Z is given,

so after halving 0.954 you'll get $\textrm{P}(0. In order to get the above value you should add 0.5 (because the graph is symmetrical around P(z) axis)
• Aug 31st 2011, 04:05 PM
Paymemoney
Re: Normal Distribution question
How would i find the quartiles of the standard normal distribution?

i know that there it is split into three sections, but how do i calculate the percentages
• Aug 31st 2011, 06:49 PM
mr fantastic
Re: Normal Distribution question
Quote:

Originally Posted by Paymemoney
How would i find the quartiles of the standard normal distribution?

i know that there it is split into three sections, but how do i calculate the percentages

Rview the definition of a quartile. Then apply what you learned so far in this thread.