Six Sigma Statistical Terms - II

Six Sigma Statistical Terms
CENTER LINE
The line on a statistical process control chart which represents the characteristic’s central tendency.

CENTRAL TENDENCY
Numerical average, e.g., mean, median, and mode; center line on a statistical process control chart.

CHAMPION
An executive level business leader who facilitates the leadership, implementation, and deployment of Six Sigma philosophies.

CHANGE ACCELERATION
A process which helps accelerates stakeholder buy-in and PROGRAM PROGRAM (CAP) implementation of new philosophies and processes within a business.

CHARACTERISTIC
A definable or measurable feature of a process, product, or service.

CLASSIFICATION
Differentiation of variables.

COMMON CAUSE
See RANDOM CAUSE

CONFIDENCE LEVEL
The probability that a randomly distributed variable “x” lies within a defined interval of a normal curve.

CONFIDENCE LIMITS
The two values that define the confidence interval.

CONFOUNDING
Allowing two or more variables to vary together so that it is impossible to separate their unique effects.

CONSUMERS RISK
Probability of accepting a lot when, in fact, the lot should have been rejected (see BETA RISK).

CONTINUOUS DATA
Data obtained from a measurement system which has an infinite number of possible outcomes.

CONTINUOUS RANDOM
A random variable which can assume any value VARIABLE continuously within some specified interval.

CONTROL CHART
A graphical rendition of a characteristic’s performance across time in relation to its natural limits and central tendency.

CONTOL LIMITS
Apply to both range or standard deviation and subgroup average (X) portions of process control charts and are used to determine the state of statistical control. Control limits are derived statistically and are not related to engineering specification limits in any way.

CONTROL PLAN
A formal quality document that describes all of the elements required to control variations in a particular process or could apply to a complete product or family of products.

CONTROL SPECIFICATIONS
Specification requirements for the product being manufactured.

CORRELATION
The relationship between two sets of data such that when one changes, the other is likely to make a corresponding change. Also, a statistical tool for determining the relationship between two sets of data.

COST OF POOR QUALITY
Cost associated with providing poor quality products or (COPQ) services. Can be divided into four cost categories: Appraisal, Scrap, Rework, and Field Complaint (warranty costs).

CRITICAL TO QUALITY (CTQ)
A drawing characteristic determined to be important for CHARACTERISTIC variability reduction based on a requirement from production, engineering, customer application, or regulatory agency. Can also apply to transactional or service delivery processes.

CUT OFF POINT
The point which partitions the acceptance region from the reject region.

DATA
Factual information used as a basis for reasoning, discussion, or calculation; often refers to quantitative information.

DATA TRANSFORMATION
A mathematical technique used to create a near normally distributed data set out of a non-normal (skewed) data set.

DEFECT
Any product characteristic that deviates outside of specification limits.

DEFECT PER MILLION
Quality metric used in the Six Sigma process and is OPPORTUNITIES (DPMO) calculated by the number of defects observed divided by the number of opportunities for defects normalized to 1 million units.

DEGREES OF FREEDOM
The number of independent measurements available for estimating a population parameter.

DENSITY FUNCTION
The function which yields the probability that a particular random variable takes on any one of its possible values.

DEPENDENT VARIABLE
A Response Variable; e.g., y is the dependent or “Response” variable where Y = f(X1. . .XN) process input variables.

DESIGN OF EXPERIMENT
A formal, proactive method for documenting the selected (DOE) controllable factors and their levels, as well as establishing blocks, replications and response variables associated with a planned experiment. It is the plan for conducting the experiment and evaluating the results.

DISCRETE DATA
Data obtained from a measurement system which has a finite number of possible outcomes.

DISCRETE RANDOM VARIABLE
A random variable which can assume values only from a definite number of discrete values.

DISTRIBUTIONS
Tendency of large numbers of observations to group themselves around some central value with a certain amount of variation or “scatter” on either side.