In the social sciences, a paradigm is a theory that has come to be generally accepted as the way to do research in a given field. A paradigm designates what kinds of issues are going to be researched and how (what sorts of tools will be used, etc) those issues will be investigated.
As an example of this, one can argue that there are two competing paradigms within the discipline of political science in the US. One of these is a quantitative approach and the other is more traditional. The two paradigms differ with one another most clearly on what tools to use. The quantitative people believe that political science research should be based on numbers and statistical analyses of those numbers. This encourages them to look at questions that tend to produce a lot of data. By contrast, the other paradigm relies more on interviews, opinions, and theories. It does not aspire to be a hard science and it asks questions that are more about ideas than about numbers.