x Turn on thread page Beta
 You are Here: Home >< Maths

# Statistics watch

1. What is the probability that 1 egg weighs less than 49 grams? Call this probability . Then the probability that exactly three eggs weight less than 49 grams is where .
2. (Original post by Zacken)
What is the probability that 1 egg weighs less than 49 grams? Call this probability . Then the probability that exactly three eggs weight less than 49 grams is where .
Can i show what ive done first?
3. (Original post by Ayaz789)
Can i show what ive done first?
Why didn't you put that in the OP?
4. So ive done P(0>3Y-X)
3Y-X -N(54-50, 1.2^2 +2^2)
E(3Y-X)=(4,5.44)
Is that right so far?
5. (Original post by Zacken)
Why didn't you put that in the OP?
Because i think you have done it a different way to me
6. (Original post by Ayaz789)
So ive done P(0>3Y-X)
3Y-X -N(54-50, 1.2^2 +2^2)
E(3Y-X)=(4,5.44)
Is that right so far?

What you've done is fine - yes (except check your variance! It's wrong). Although I have no clue why you're finding E(3Y-X) in the last line.

So you have (I'll call it W to make it more obvious) and you want .

Well, that's a simple normal distribution problem now. Can you see what to do from here?
7. (Original post by Zacken)

What you've done is fine - yes. Although I have no clue why you're finding E(3Y-X) in the last line.

So you have (I'll call it W to make it more obvious) and you want .

Well, that's a simple normal distribution problem now. Can you see what to do from here?
The thing is in the mark scheme it says E(3Y-X)= (4,16.96) Where do they get 16.96 from? And do you use z=x-mean/ (standard deviation)
8. (Original post by Ayaz789)
The thing is in the mark scheme it says E(3Y-X)= (4,16.96) Where do they get 16.96 from? And do you use z=x-mean/ (standard deviation)
If it says that, then it's wrong.

.

So . Then yeah, use z = x - mean / standard dev.
9. (Original post by Zacken)
If it says that, then it's wrong.

.

So . Then yeah, use z = x - mean / standard dev.
Okay thanks
10. (Original post by Ayaz789)
Okay thanks
Sure.

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 28, 2016
Today on TSR

### Loughborough better than Cambridge

Loughborough at number one

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