Common (natural) variation
attributed to design of the process and affect all output of the process. (part of process design).
Methods, machines, personnel, and environment.
Assignable (special) variation
events or actions that are not part of the process design. They can be traced to a specific reason.
A process in control ONLY exhibits
common vatiation
Random Variation
centered around a mean and occurs with a somewhat consistent amount of variation.
Process Charts
graphs designed to signal process workers when nonrandom variation is occurring
Variable
continuous measurement such as weight, height, or volume
Attribute
either or situation"
Motor is either starting or not starting
X bar chart
monitor the average of the characteristic being measured
R chart
monitors the dispersion of the process
Process capability
the capability of a process to produce a product that meets specification
Population
a collection of all the items or observations
Sample
subset of the population
Sampling distributions
distributions that reflect the distributions of sample means