Probability distribution questions

Click For Summary
SUMMARY

The discussion focuses on solving probability distribution problems involving uniform and normal distributions. The first problem requires calculating P(X+Y+Z<1) for independent random variables X, Y, and Z uniformly distributed over a unit cube. The second problem involves finding the distribution of Y=(X1^2+X2^2+X3^2)^(1/2) where X1, X2, and X3 are independent normal variables. The participants emphasize the importance of correctly setting up integrals and understanding the distribution of squared normal variables.

PREREQUISITES
  • Understanding of uniform distribution in probability theory
  • Knowledge of normal distribution and its properties
  • Familiarity with triple integrals in multivariable calculus
  • Concept of chi-squared distribution related to sums of squared normal variables
NEXT STEPS
  • Study the geometric interpretation of the region defined by X+Y+Z<1 in a unit cube
  • Learn about the chi-squared distribution and its applications
  • Explore the transformation of random variables, specifically for Y=X^2
  • Investigate the properties of independent normal variables and their sums
USEFUL FOR

Students in statistics, mathematicians, and data scientists who are working with probability distributions and require a deeper understanding of uniform and normal distributions in practical applications.

indigogirl
Messages
8
Reaction score
0

Homework Statement


1. If X, Y, and Z have uniforj density of 1 on unit cube, then find P(X+Y+Z<1)
2. X1, X2, and X3 are independent and normal. Find distribution of Y=(X1^2+X2^2+X3^2)^(1/2)

The Attempt at a Solution



1. I set up a triple integral, but I'm not sure if I got the limits right... P(X+Y+Z<1)=int from 0 to 1, int from y to 1-x, and int from z to 1-x-y... Then I integrated it, but I'm left with the variable z in the answer, which I think is wrong.

2. really not sure
 
Physics news on Phys.org
1. Are you integrating z from z to 1-x-y? This doesn't make sense, does it? If x and y are fixed, the maximum value of z is indeed 1-x-y; what is the minimum value of z?

2. Try something simpler. If x is independent and normal, what is the distribution of y=x^2?
 
1. Easier to visualize the region over which X+Y+Z<1 (in addition to X, Y, Z all being > 0). The ratio of the region to the volume of the unit cube is the answer.

2. You could start by finding the dist. of Y^2=X1^2+X2^2+X3^2. Which distribution describes the sum of squared normal variables?
 

Similar threads

Replies
9
Views
3K
Replies
7
Views
1K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
6
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
6
Views
2K
Replies
2
Views
2K
Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 9 ·
Replies
9
Views
3K