A process can be defined as a combination of components, tools, people and machines that together produce an item, like a part that subsequently is inserted into a finished good item. Although, the output of the process may vary, the final customer requires the product to satisfy the standards specified by the engineers. Management’s goal is to control the output units of a process so that it conforms to the standards set by the engineers. The output measures are of two types: attribute or variable. Attribute is when the output measure is defective or not defective. Variable is when some measure is taken from each sampled unit.