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The joint density function of X and Y isf(x,y)=x+y0<x<1,0<y<100otherwise

(a) Are X and Y independent?

(b) Find the density function of X.

(c) FindP[X+Y<1].

Short Answer

Expert verified

a. X and Y are not independent.

b. The density function of X is

fX(x)=x+12;0<x<1

c. The value of P[X+Y<1]=23

Step by step solution

01

Content Introduction

X and Y are random variables with a combined density function.

02

Explanation (Part a)

The joint density function of X and Y is

fX,Y(x,y)=x+y;0<x<1and0<y<1

FormarginaldensityofX,pleaserefferpart(b)forexplanationfX(x)=x+0.5;0<x<1Thereforebysymmetry,forY,wehavefY(y)=y+0.5;0<y<1(x+12)(y+12)x+yWhichprovesthatxandyaredependent.

03

Explanation (Part b)

The marginal density of X is

fX(x)=01(x+y)dy=xy+y2201=x+12

x+120<x<1

04

Explanation (Part c)

P[X+Y<1]=x=01y=01-xfX,Y(x,y)dydx=0101-x(x+y)dy=01xy+y2201-xdxUponsimplification,weobtain=01x2+12dx=x36+x201=23

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