The easy way to confirm (and manage) your "stats" users is to go to the Control Panel -> Statistics -> Site Statistics page, and click on the number of users link in the "Users" column adjacent to your domain name.
This is display your current "stats" users and let you add new users. You can then check the user" password from the Users section of the control panel.
Additionally, you could change the user's password by clicking "edit" in the display stats users screen, but that might create confusion as you will have changed the password for all that users' functions.
Usually, when you see what user is authorized for stats, it is enough to remind you of the current password for that user, or you can look it up as described.
You can add additional stats users from these screens also. Good Luck!