You are Here: Home >< Maths

# S2 Normal Distribution help

Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016
1. Hi, I came across this question in the ocr textbook and I'm a bit stuck. Could someone show me how to do it please? It's from Ex 2B p.34

7 (e) Given that X~N(15,4), find s,t,u,v and w correct to 2 d.p.

P(|X-15| < w) = 0.9

The answer is 3.29 but I don't know how to get there!
Thanks very much
2. (Original post by Cometflute)
Hi, I came across this question in the ocr textbook and I'm a bit stuck. Could someone show me how to do it please? It's from Ex 2B p.34

7 (e) Given that X~N(15,4), find s,t,u,v and w correct to 2 d.p.

P(|X-15| < w) = 0.9

The answer is 3.29 but I don't know how to get there!
Thanks very much
What have you tried?
3. (Original post by RDKGames)
What have you tried?
I know that you use z=(x-15)/2 and 15 is the mean so the graph should be like the Z graph except a different height. I tried doing P(|X-15|<w) = 2x P(Z<w) -1 so P(X<w/2) = P(Z<1.282) but that didn't give me the right answer. Maybe you're meant to introduce s= |X-15| for example? But I'm still not sure how to go about solving that...

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: September 25, 2016
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:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams