MGOC20H3 Lecture Notes - Lecture 5: Control Chart, Central Limit Theorem, Test Plan
Document Summary
Automotive study indicates japanese transmissions have less variability and hence lower warranty costs. Natural variations: also called common causes (background noise, white noise), affect virtually all production processes, expected amount of variation, output measures follow a probability distribution, for any distribution there is a measure of central tendency and dispersion. If distribution of outputs falls within acceptable limits, process is said to be in control . Assignable variations: also called special causes of variation. Generally this is some change in the process: variations that can be traced to a specific reason. Example: improperly adjusted machines, operator errors, defective raw materials: the objective is to discover when assignable causes are present, eliminate the bad causes, incorporate the good causes. If only natural causes of variation are present, the output of a process forms a distribution that is stable over time and is predictable.
