Instructions
Visit Bungie's website. (See Resources).
Click the "Log In" button at the top right of the website. This directs you to a page to sign in to your Windows Live account, which you created when you set up your Xbox Live account.
Enter your email address and password and click "Sign In." Bungie's website will reappear.
Hold your mouse over the "Profile" option near the top right of the website. Options appear in a drop-down menu.
Click "Career Stats." Your "Halo" stats will appear.
Click the game type for which you want to learn your kills-to-deaths ratio, such as "Competitive," "Invasion" or "Arena," and the stats will appear.
View the "Kill/Death" line beneath the "Games Played" pie graph.