# How to find certain percentile of X

• Nov 2nd 2008, 07:15 AM
dingdong
How to find certain percentile of X
Given that fx(x) = 0 (x <= 10)
= 10/x^2 (x >10)

Find the 60-th percentile of X.

How do we solve this?
• Nov 2nd 2008, 02:18 PM
CaptainBlack
Quote:

Originally Posted by dingdong
Given that fx(x) = 0 (x <= 10)
= 10/x^2 (x >10)

Find the 60-th percentile of X.

How do we solve this?

You have to solve the equation:

$\int_{-\infty}^x f(\xi)\ d\xi=0.6$

In this case this reduces to solving:

$\int_{10}^x \frac{10}{\xi^2}\ d\xi=1-\frac{10}{x}=0.6$

CB