6. Basic Statistics NORMAL DISTRIBUTION Approximately 99.7% of the data (or virtually all) are between +/- 3 standard deviations from the mean when data is normally distributed. Mean -1s +1s 99.7% -2s +2s -3s +3s
7. Process Capability LSL USL Poor Process Capability! Off Center, Spread Too Wide LSL USL Fair Process Capability! Off Center, Tight Spread LSL USL Fair Process Capability! Centered, Spread Too Wide LSL USL THE MISSION: Excellent Process Capability! Centered, Tight Spread Centering and Spread are critical components of Process Capability!
8. Process Capability Process Capability Statistics The formula: USL - X Cpk-upper = 3 Cpk-overall = X – LSL min {Cpk-up, Cpk-lo} Cpk-lower = 3 *Note: we are working with continuous data only when computing a Cpk