# Thread: Standard Norm. Distribution Curves

1. ## Standard Norm. Distribution Curves

Ive been studying for a test ive got tomorrow, and i keep getting stuck on questions that i should know by now.-_-. heres some of them.

Find the z value to the right of the mean so that:
a. 53.98% of the area under the distribution curve lies to the left of it.
b. 71.90% ' '
c. 96.78% ' '

Im using my TI-84 but i also have a normal distribution chart thing. I wasnt sure how to approach this kind of problem. I have a memory of doing them in class, but once im out of class its over.--_--

thanks for the help

2. Originally Posted by hemoglowen
Ive been studying for a test ive got tomorrow, and i keep getting stuck on questions that i should know by now.-_-. heres some of them.

Find the z value to the right of the mean so that:
a. 53.98% of the area under the distribution curve lies to the left of it.
b. 71.90% ' '
c. 96.78% ' '

Im using my TI-84 but i also have a normal distribution chart thing. I wasnt sure how to approach this kind of problem. I have a memory of doing them in class, but once im out of class its over.--_--

thanks for the help
In each case you can use the invnorm command.

You must have been shown how to do this ..... Go back to your class notes or textbook and review it.

3. ahh thats right. invnorm. thanks a bunch! In my scurry of mass studying, ive seemed to misplaced about three pages of my notes. if you dont mind me asking, what do i enter in the inverse normal command? is it the number given, which is 53.98% and the number left over from 100%? which would be 46.02%

so, invrnorm(.5398,.4602)
this gives me the answer of .5601

by the way, thanks for the help so far.

4. Originally Posted by hemoglowen
ahh thats right. invnorm. thanks a bunch! In my scurry of mass studying, ive seemed to misplaced about three pages of my notes. if you dont mind me asking, what do i enter in the inverse normal command? is it the number given, which is 53.98% and the number left over from 100%? which would be 46.02%

so, invrnorm(.5398,.4602)
this gives me the answer of .5601

by the way, thanks for the help so far.
To get the value of z when you know Pr(Z < z)= a:

The format of the command is as follows:

invNorm(a, mean, standard deviation).

In the absence of mean and standard deviation the calculator defaults to the standard normal.

5. Originally Posted by mr fantastic
To get the value of z when you know Pr(Z < z)= a:

The format of the command is as follows:

invNorm(a, mean, standard deviation).

In the absence of mean and standard deviation the calculator defaults to the standard normal.

awesome, thanks. that was pretty much all i needed. maybe i should have asked for the format of the command like you said. Thanks again!
hemoglowen