How can I tell if Windows 8 users have a tablet or PC?
Google Analytics has a filter for Tablet (click "Mobile Device" and look at the second row), which will help determine whether Windows 8 users are using a tablet or PC.
To compare these two segments, go to:
Standard Reports -> Audience -> Mobile -> Devices
Then:
1.) Click the down arrow just above the Explorer tab
2.) Click the Create New Segment button
3.) Click Technology
4.) For Operating System select Windows
5.) For Operating System Version select 8
6.) Scroll down to Mobile (Including Tablet) and check No
7.) Specify the segment name at the top (above Demographics) as "Windows 8 Desktop Users" and click Save.
Next, to view Windows 8 tablet users:
8.) Repeat steps 1-6, but check Yes in step 6.
9.) Then under Advanced -> Conditions, click on the Ad Content button and select: Visitors -> Tablet and chose Yes.
10.) Specify the segment name as "Windows 8 Tablet Users" and click Save.
While viewing these segments, you can can click the Add to Dashboard button to add them to your Dashboard for quicker access.
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Side note: For Internet Explorer user-agents for tablets, you should likely include those for ARM-based Windows RT models too, which do not contain the string "Touch" in them, but are touch-enabled. Also "Touch" can apply to all-in-one PC's that are touch-enabled too (not just tablets).