Studies show that many organisations face a deficient capability of information analysis to make decisions effectively, due to a lack of statistical evidence and the poor quality of data, among other factors. This has become an increasing problem in some public organisations of developing countries. This study proposes a methodical approach for the policy formulation improvement, based on statistical evidence. Conducted as a case study in the city of Barrancabermeja in Colombia, this work identified relevant factors that influence the approval procedure, tested as statistical evidence at a confidence level ? = .05. The sample consisted of 55 civil engineering projects completed during 2008?2013. The statistical evidence found in this study suggest a benchmark of 15 days as the expected duration for the registration and approval processes of projects, which may be adopted as an assessment policy for public project management in Colombia. Additionally, the study provided statistical evidence to formulate policy related with: the memorandum of commitment to the community benefited by the project, the methodology for the registration of public projects, and the project budget estimation. Thus, this study advocates the use of statistical evidence as an appropriate strategy for the improvement policy formulation of project management processes and decision making in public organisations.