statistical symbols in microsoft word

I've spent like 5 hours trying to figure out how to insert a bar (called overstrike or overline) over a word ... like the bar that goes over x for "mean" ... but I have to put the bar over the word "pred" in the results section of my dissertation. I've tried to use the formula function but when I press alt F9 to execute "the result" (of the equation), the equation disappears and there is no "result." I am using microsoft office 2013 though I'd assume instructions on how to do this in earlier versions would be helpful and lead me in the right direction. PLEASE HELP! Thanks for any infor or advice you can offer!