Empirical research is any research that bases its findings on direct or indirect observation as its test of reality. Such research may also be conducted according to hypothetico-deductive procedures, such as those developed from the work of R. A. Fisher.
The researcher attempts to describe accurately the interaction between the instrument (or the human senses) and the entity being observed. If instrumentation is involved, the researcher is expected to calibrate her/his instrument by applying it to known standard objects and documenting the results before applying it to unknown objects.
In practice, the accumulation of evidence for or against any particular theory involves planned research designs for the collection of empirical data, and academic rigor plays a large part of judging the merits of research design. Several typographies for such designs have been suggested, one of the most popular of which comes from Campbell and Stanley (1963). They are responsible for popularizing the widely cited distinction among pre-experimental, experimental, and quasi-experimental designs and are staunch advocates of the central role of randomized experiments in educational research.