Quality Assurance (QA): The function of software quality that assures that the standards, processes, and procedures are appropriate for the project and are correctly implemented. Statistical Tools & Techniques can be applied in both Quality Assurance & Quality Control. When they are applied to processes (process inputs & operational parameters), they are called Statistical Process Control (SPC) & it becomes the part of Quality Assurance. Quality Control (QC): The function of software quality that checks that the project follows its standards, processes, and procedures, and that the project produces the required internal and external (deliverable) products. When statistical tools & techniques are applied to finished products (process outputs), they are called as Statistical Quality Control (SQC) & comes under Quality Control.