# Find the cumulative and probability density functions

• Mar 23rd 2010, 10:59 PM
My Little Pony
Find the cumulative and probability density functions
Anyone know how I can get this question started?

What does the 'max' function mean?
• Mar 24th 2010, 12:02 AM
matheagle
max means maximum or largest of the three

$P(Y\le x)=P(X_1\le x, X_2\le x, X_3\le x)$

use independence.....

$=P(X_1\le x)P(X_2\le x)P(X_3\le x)$

now use your distribution function for the exponential.
• Mar 24th 2010, 12:03 AM
mr fantastic
Quote:

Originally Posted by My Little Pony
Anyone know how I can get this question started?

What does the 'max' function mean?

Use Google to research Order Statistics (you will also find many relevant threads in this subforum using the Search tool).
• Mar 24th 2010, 11:31 AM
My Little Pony
I got:

(1 - exp(-theta*x))^3 as the cdf and 3*theta*exp(-theta*x)*(1 - exp(-theta*x) as the pdf.

Can someone verify if this is correct?