ISDS 3115-Chapter 6S "Statistical Process Control"
The quality level of a lot considered good
Acceptable Quality Level (AQL)
A method of measuring random samples of lots or batches of products against predetermined standards
Acceptance Sampling
Variation in a production process that can be traced to specific causes
Assignable Variation
The % defective in an average lot of goods inspected through acceptance sampling
Average Outgoing Quality (AOQ)
The quality level of a lot considered bad
Lot Tolerance % Defective (LTPD)
Variability that affects every production process to some degree and is to be expected; also known as Common Cause
Natural Variations
The theoretical foundation for x-charts, which states that regardless of the distribution of the population of all parts or services, the distribution of x's tends to follow a normal curve as the number of samples increases
Central Limit Theorem
The mistake of a customer's acceptance of a bad lot overlooked through sampling
Consumer's Risk
A graphical presentation of process data over time
Control Chart
A ratio for determining whether a process meets design specifications; a ratio of the specification to the process variation
Cp
A proportion of variation (3o) between the center of the process and the nearest specification limit
Cpk
A graph that describes how well an acceptance plan discriminates between good and bad lots
Operating Characteristic (OC) Curve
The ability to meet design specifications
Process Capability
The mistake of having a producer's good lot rejected through sampling
Producer's Risk
A control chart that tracks the "range" within a sample; it indicates that a gain or loss in uniformity has occurred in dispersion of a production process
R-Chart
A test used to examine the points in a control chart to see if nonrandom variation is present
Run Test
A process used to monitor standards by taking measurements and corrective action as a product or service is being produced
Statistical Process Control (SPC)
Statistically, the probability of rejecting a good lot
Type I Error
Statistically, the probability of accepting a bad lot
Type II Error
A quality control chart for variables that indicates when changes occur in the central tendency of a production process
X-Chart
A quality control chart used to control the number of defects per unit of output
c-Chart
A quality control chart that is used to control attributes
p-Chart