13.07.2014 Views

November 2001 - Course 1 SOA Solutions

November 2001 - Course 1 SOA Solutions

November 2001 - Course 1 SOA Solutions

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

7. A<br />

Cov C , C = Cov X + Y, X + 1.2Y<br />

( 1 2) ( )<br />

= Cov ( X, X) + Cov ( Y, X) + Cov ( X,1.2Y) + Cov( Y,1.2Y)<br />

= Var X + Cov ( X, Y) + 1.2Cov ( X, Y)<br />

+ 1.2VarY<br />

= Var X + 2.2Cov ( X, Y)<br />

+ 1.2VarY<br />

( ) ( ( ))<br />

2<br />

( ) ( E Y )<br />

2 2<br />

2<br />

Var X = E X − E X = 27.4 − 5 = 2.4<br />

VarY<br />

2 2<br />

= E Y − ( ) = 51.4 − 7 = 2.4<br />

( X + Y) = X + Y + ( X Y)<br />

Var Var Var 2Cov ,<br />

1<br />

Cov ( XY , ) = Var ( X+ Y)<br />

−Var X−VarY<br />

2<br />

1<br />

= ( 8 − 2.4 − 2.4 ) = 1.6<br />

2<br />

Cov , = 2.4 + 2.2 1.6 + 1.2 2.4 = 8.8<br />

( C C ) ( ) ( )<br />

1 2<br />

( )<br />

<strong>Course</strong> 1 <strong>Solutions</strong> 4 <strong>November</strong> <strong>2001</strong>

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!