How can I create or insert the "x bar" or mean symbol in Word 2011 for Mac?

The simplest method is to use the Equation Editor on the Document Elements tab of the Ribbon. Once you click the Equation [Σ] button:

1. Click the Accent [ä] button
2. Scroll to & select the Overbar character
3. Left Arrow into the box under the bar
4. Type either an upper or lower case letter of your choice
5. Click outside the Equation field

If you'll need to use the overbar character frequently you can select it then use Edit> Paste Special - Picture. As a picture or as an EQ object it can be saved as a new equation (using the button on the right edge of the EQ control), added to the Scrapbook, saved as an AutoText Entry or as an AutoCorrect Item.

Regards,

Bob J.

Whatever method you try, it is important that you verify that the method does the stuff you need - e.g. displaying, printing etc. For example, many methods may only work in Word, or on Mac, or in Mac Word, or depending on what fonts are available. Some methods (probably most) won't result in a character that you can rely on to display properly in a web page.

You can consider using "Math Autocorrect". Go to Tools->Autocorrect...->Math autocorrect, ensure that "Use Math AutoCorrect rules outside of math regions" is checked, then in your Word document, type

x\bar

followed by a space. The \bar should change to a bar over the x.

Some Unicode letters have a macron version, but not all (x is one of them).  You may be able to get macron-x by

a. inserting an x

b. from the Mac character viewer, dragging the Combining macron character into the document just after the x. It's Unicode character U+0304. Looking at the result, the macron is not quite central over the letter, so maybe that's what you already tried.

Suzanne Barnhill has a page at http://wordfaqs.mvps.org/overbar.htm with some suggestions, one of which involves using an EQ field in the document. That should also work in Mac Word, but the instructions may be slightly different.

You can also consider using Insert->Equation to insert an equation, using he appropriate "Accent" structure to insert a "box with accent". Then insert the character you want in the box.