A response to Storm and Ertel (2002)

Storm and Ertel (2001) published a meta-analysis of 79 ganzfeld studies published between 1974 and 1996. They used substantially inconsistent inclusion criteria to form the database and included studies with well-documented methodological problems. Using a methodological quality scale that omitted important items such as the use of duplicate target sets, they assessed only 11 of the 79 studies and weighted those 11 studies by the quality scores. They claimed that the highly statistically significant cumulated outcome represented strong evidence for psi. As the authors (Milton & Wiseman, 2001) argued in their earlier response, the inclusion of a large proportion of studies with methodological problems and the inconsistent methods of handling studies make it impossible to interpret the cumulated probability at face value.