According to McCombs and Shaw, public agenda is the most important public issues as measured by public opinion surveys. This information can be found on page 361 in chapter 28 of our textbook.
While McCombs and Shaw did their own survey to find out what the most important issues, most of the public surveys are done through mass media so it is usually biased anyways. I can see what McCombs and Shaw were trying to prove; they were trying to prove that one affects the other, but I don't feel this is true in they way it should be. I think that the media played a huge part in people's opinions about what is the most important public issues, but I think it should be the other way around. I feel that people's opinions on what is most important should shape the media's agenda.
~Tornn