It probably varies in the details company-to-company. To get some ideas of what other companies do, try a Google search for "job description QA Engineer" or similarly worded searches and you can probably get some idea of how specific/general they are.
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Mike S. ("Gun Nut")
And they ask me why I drink....
Another option is to look at some of the different Job sites (such as hotjobs, monster, etc....). Some of them list various job descriptions under their salary calculators. Also the ASQ website has a very brief description for a Quality engineer. You can also try looking through the help wanted ads, some place list pretty detailed descriptions in their ads. Hope this helps.