You are Here: Home >< Maths

# Continuous Random Variables s2 watch

1. 40cm ribbon is cut into two at a random point. The R.V. 'X' represents length of the shorter piece in cm.

Specify the probability distribution of X.

Bit stuck. All I can work out is that the distribution is continuous because X could have like 10000 decimal places so it's not discrete, and that P(0<X<20) = 1 as otherwise it's a negative length or it's not the shortest ribbon.

Can anyone nudge me in the right direction?
2. (Original post by Fudge2)
40cm ribbon is cut into two at a random point. The R.V. 'X' represents length of the shorter piece in cm.

Specify the probability distribution of X.

Bit stuck. All I can work out is that the distribution is continuous because X could have like 10000 decimal places so it's not discrete, and that P(0<X<20) = 1 as otherwise it's a negative length or it's not the shortest ribbon.

Can anyone nudge me in the right direction?
the required distribution is uniform continuous (Rectangular) distributed over the interval [0,20]

do you know how to specify the pdf?
3. (Original post by TeeEm)
the required distribution is uniform continuous (Rectangular) distributed over the interval [0,20]

do you know how to specify the pdf?
Is specifying it where I would say f(x) = 1/20 for 0<x<20 and 0 otherwise? At least I think that's what it would be?

So it's rectangular because the probability of cutting it at any point is the same as cutting it at any other point if that makes sense?

Thanks
4. Goodness, that's a badly worded question! Strictly speaking there isn't enough information to answer it. Cut at a "random" point does not imply cut at a uniformly distributed random point...
5. (Original post by Fudge2)
Is specifying it where I would say f(x) = 1/20 for 0<x<20 and 0 otherwise? At least I think that's what it would be?

So it's rectangular because the probability of cutting it at any point is the same as cutting it at any other point if that makes sense?

Thanks
correct
6. (Original post by Gregorius)
Goodness, that's a badly worded question! Strictly speaking there isn't enough information to answer it. Cut at a "random" point does not imply cut at a uniformly distributed random point...
standard current A level vocabulary
7. (Original post by TeeEm)
standard current A level vocabulary
Oh my. No wonder I have reprogramme students when they arrive at university
8. (Original post by Gregorius)
Goodness, that's a badly worded question! Strictly speaking there isn't enough information to answer it. Cut at a "random" point does not imply cut at a uniformly distributed random point...
Haha yeah I struggled to make the connection! Glad it isn't just me who thought it was weird

(Original post by TeeEm)
correct
Awesome thanks. I can't rep you apparently so PRSOM.

### Related university courses

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: November 4, 2015
Today on TSR

### Edexcel C3 Maths Unofficial Markscheme

Find out how you've done here

### 3,774

students online now

Exam discussions

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