Purpose: The National Prescribing Service Ltd (NPS) aims to improve prescribing and use of medicines consistent with evidence-based best practice. This study compares two statistical methods used to determine whether multiple educational interventions influenced antibiotic prescribing in Australia. Methods Monthly data (July 1996 to June 2003) were obtained from a national administrative claims database. The outcome measures were the median number of antibiotic prescriptions per 1,000 consultations for each general practitioner (GP) each month, and the mean proportion (across GPs) of each …