You are Here: Home >< Maths

# S1 normal distribution Watch

1. how are you meant to now if you are meant to do 1- phi(z)

the normal case is when the value of z= -... then you have to do 1-phi(z)
but when the value of z= +.... , when do you do 1- phi(z)

any help would be appreciated thanks
2. If you have standardised/normalised your data, then it is now in terms of 'x' and you are now working out say

P(Z < z) = phi(z).

Correctly, you said P(Z < -z) = phi(-z) = 1 - phi(z).

Also, if you wanted to do P(Z > z) then you would also do 1 - P(Z < z) = 1 - phi(z).

Why? If you look at your graph of the standard Normal distribution, because it is symmetric, you get that these two values are the same.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 14, 2013
Today on TSR

### Who's off because of the weather?

What's it like where you are?

### I hate Christmas

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.