The evidence pyramid (image above) visually depicts the evidential strength of different research designs. Studies with the highest internal validity, characterized by a high degree of quantitative analysis, review, analysis, and stringent scientific methodology, are at the top of the pyramid. Observational research and expert opinion reside at the bottom of the pyramid. In evidence-based practice the systematic review is considered the highest level of information and is at the top of the pyramid. (The pyramid was produced by HLWIKI Canada and is CC).