The case for using mixed methods for designing, implementing, and disseminating evidence-based interventions for public health practice.

A well-recognized gap exists between findings from public health research and their use in public health practice to improve outcomes. The World Health Organization (WHO) has identified implementation research as vital to improving the adaptation and dissemination of public health interventions into real-world settings. Implementation research encompasses multimethod evaluation approaches; 'mixed methods', the planned integration of qualitative and quantitative methods, is a key tool. We argue that mixed methods designs are crucial for design and evaluation of public health interventions, provide illustrative case studies, discuss key analytic approaches in mixed methods design, identify resources for mixed methods research and advocate for more training. On behalf of the International Network for Epidemiology in Policy (INEP), an international non-profit organization of 24 member societies that promotes the development of equitable, evidence-based health policies, we call for increased collaboration between qualitative and quantitative research teams to improve the design and evaluation of public health interventions.