Meta-Analysis
A meta-analysis basically a study of studies. Instead of doing new research, a scientist compares the results of different studies done in different ways at different times and in different places. The purpose is to find results that may have been missed or masked by the limitations of individual studies. A good example is a recent meta-analysis that looked at dozens of dietary studies and found a result that had been missed by numerous individual dietary studies - that eating more foods with calcium helps you lose weight.