# Finding the cdf

Printable View

• Apr 23rd 2008, 08:41 PM
cirrus74
Finding the cdf
http://i235.photobucket.com/albums/e...untitled-2.jpg

Find the expression for the cdf $\displaystyle F_x(x)$

We were actually given the solutions:

http://i235.photobucket.com/albums/e...untitled-3.jpg

I understand the first part, concerning where x<0 but I don't understand when $\displaystyle x\geq 0$; why do we take the limits and equation from when x<0 + the limits and equation for $\displaystyle x\geq 0$

Please explain this to me. Thanks.
• Apr 23rd 2008, 09:20 PM
mr fantastic
Quote:

Originally Posted by cirrus74
http://i235.photobucket.com/albums/e...untitled-2.jpg

Find the expression for the cdf $\displaystyle F_x(x)$

We were actually given the solutions:

http://i235.photobucket.com/albums/e...untitled-3.jpg

I understand the first part, concerning where x<0 but I don't understand when $\displaystyle x\geq 0$; why do we take the limits and equation from when x<0 + the limits and equation for $\displaystyle x\geq 0$

Please explain this to me. Thanks.

If x > 0 then $\displaystyle F_X (x) = \Pr(X < x) = \int_{-\infty}^{0} f(x) \, dx + \int_{0}^{x} f(x) \, dx = .....$