Rosenthal, Robert and Donald B. Rubin. 1979. "Comparing Significance Levels of Independent Studies." Psychological Bulletin 86, no. 5: 1165-1168.
Methods for comparing two or more statistical significance (p) levels are described; these methods are more rigorous, systematic, and informative than the comparisons that are commonly made by using a significant/not significant dichotomy. Formulas are provided for calculating the significance level of a comparison between two or more p levels.