As in any multidisciplinary domain, there are many ways of conducting research. The five main methods used in parapsychology are ~
~Scholarly research, including discussion of philosophical issues and historical surveys.
~Analytical research, including statistical analysis of large databases.
~Case studies, including in-depth studies of personal psi experiences, field investigations, and comparisons of cross-cultural beliefs and practices related to psi.
~Theoretical research, including mathematical, descriptive and phenomenological models of psi.
~Experimental research, including laboratory studies of psi effects.
Although all five of these approaches contribute to the field, today the primary source of “hard evidence” in parapsychology is controlled laboratory experiments. By applying the exacting standards of scientific method, researchers over the past six decades have developed an increasingly persuasive database for certain types of psi phenomena.
Several major experimental designs have been developed during this time, and a select few experiments have now been repeated hundreds of times by dozens of researchers, world-wide. Sometimes these experiments are conducted as strict replications, but more often they are conceptually similar experiments that add controls or extend the range of questions addressed.