Interpretation of the p value: A national survey study in academic psychologists from Spain.

BACKGROUND Incorrect interpretations of p values affect professionals’ decisions and jeopardize the quality of psychological interventions and the accumulation of valid scientific knowledge. This study analyzes the errors made by Spanish academic psychologists in interpreting p values. METHOD We surveyed academic psychologists about their interpretations of p values. The sample is composed of 418 academic psychologists from Spanish public universities. The mean number of years working as a university professor is 14.16 (SD = 9.39). RESULTS Our findings suggest that many academic psychologists do not know how to correctly interpret p values. The inverse probability fallacy presents the greatest comprehension problems. Methodology instructors also interpret the significance of the p value erroneously. CONCLUSIONS These results highlight the importance of the statistical re-education of professors.