Project Management Professional (PMP) and Six Sigma certifications are equally reputable and esteemed management certifications in the project management world. A PMP online certification is different from a Six Sigma professional certification. The PMP certification primarily focuses on industry-relevant skills and knowledge in managing project work, whereas Six Sigma focuses on the elimination of any potential defects within a certain process. It is commonly used as a set of tools for business process improvement and as a qualitative methodology based on statistical analysis and quality control.