On PC, use the console. From the UESP:
getAVinfo
Get Actor Value information
This will print a short list of information about the given attribute (a.k.a. actor value) of the specified target. You can select a target with the mouse, or enter the refID of the target followed by a period before the command. For example, player.getavinfo lightarmor will return information about the player's Light Armor skill, such as the base value (what it was just after character creation), any current temporary or permanent modifiers, etc.
In this case, the skill you need to check is marksman.
http://www.uesp.net/wiki/Skyrim:Console