For a Starbuck's process (chose the one you are more familiar with), list inputs (Xs) and performance measures. Indicate which inputs you view as being key, and identify those that can be controlled and those that cannot be controlled, or are not controlled, during routine operation, which are noise and which performance measures are critical.
For this assignment I would recommend constructing a process map. Your process map identifies the process steps and inputs. I have created one as an example for making a cappuccino. It is attached in both PDF and MS Visio formats for your convenience.
Inputs on the attached process ...
Constructing a process map of making a Starbucks process, how to capture inputs, and measure process performance.