CQPA flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Cp

Process potential capability index equal to specification width divided by six sigma: (USL − LSL)/(6σ). It ignores centering, so a process can have high Cp yet still produce defects.

Cpk

Process actual capability index: the minimum of the upper and lower distances from the mean to the specification limit, each divided by 3σ. It penalizes off-center processes, unlike Cp.

Repeatability

Variation observed when one appraiser measures the same part repeatedly with the same gauge under identical conditions. It reflects equipment variation within the measurement system.

Reproducibility

Variation in measurements arising between different appraisers using the same gauge on the same parts. It reflects operator or appraiser variation in the measurement system.

AQL

Acceptable Quality Level: the maximum defective rate considered acceptable as a process average for acceptance sampling. It defines the producer's risk point on an operating characteristic curve.

Cost of quality

The total of prevention, appraisal, internal failure, and external failure costs. Failure costs, especially external failures, are usually the largest and most reducible category.

Pareto principle

The observation that roughly 80 percent of effects come from about 20 percent of causes. A Pareto chart ranks causes by frequency so improvement effort targets the largest contributors first.

PDCA cycle

Plan-Do-Check-Act: a repeating improvement cycle in which a change is planned, piloted, verified against expected results, and then standardized or revised.

Standard deviation

The square root of the variance, expressing typical dispersion around the mean in the original units. Approximately 68 percent of normal data lie within one standard deviation of the mean.

Null hypothesis

The default statistical statement of no difference or no effect. It is retained unless sample evidence produces a p-value below the chosen significance level alpha.

Type I error

Rejecting a true null hypothesis, also called producer's risk or alpha. Its probability is the significance level chosen for the test, commonly 0.05.

Type II error

Failing to reject a false null hypothesis, also called consumer's risk or beta. Statistical power equals one minus beta and increases with larger sample sizes.

p-value

The probability of observing a test statistic at least as extreme as the sample result, assuming the null hypothesis is true. Reject the null when it is below alpha.

Confidence interval

A range of plausible values for a population parameter, constructed at a stated confidence level. Wider intervals accompany higher confidence levels and smaller sample sizes.

Correlation coefficient

A value from minus one to plus one measuring the strength and direction of linear association between two variables. It does not by itself demonstrate causation.

Coefficient of determination

R-squared: the proportion of total variation in the response variable explained by the regression model. Values near one indicate a strong fit to the observed data.

ANOVA

Analysis of variance: a test comparing means of three or more groups by partitioning total variation into between-group and within-group components, evaluated with an F statistic.

Central limit theorem

The sampling distribution of the mean approaches normality as sample size grows, regardless of the population shape. It underpins many control charts and confidence intervals.

Nominal data

Data consisting of unordered labels or categories such as machine type or defect code. Only counts and proportions are meaningful; averages and standard deviations are invalid.

SIPOC diagram

A high-level process map listing Suppliers, Inputs, Process steps, Outputs, and Customers. It defines process boundaries before detailed flowcharting begins.

FMEA

Failure Mode and Effects Analysis: a structured risk assessment scoring severity, occurrence, and detection for each failure mode. The product, the Risk Priority Number, ranks items for action.

Five Whys

A root cause technique that repeatedly asks why a problem occurred, typically about five times, until the underlying systemic cause is identified rather than a symptom.

Cause-and-effect diagram

Also called Ishikawa or fishbone diagram: it organizes potential causes of a problem into branches such as Man, Machine, Material, Method, Measurement, and Environment.

Control chart

A time-ordered plot of a process characteristic with a centerline and statistically derived control limits. Points beyond limits or nonrandom patterns signal special-cause variation.

Common cause variation

Inherent, stable variation produced by the process itself. It is reduced by changing the process, not by adjusting individual points or blaming operators.

Special cause variation

Unpredictable variation from an identifiable source outside the normal process, signalled by control chart rules. It requires investigation and removal of the specific cause.

Process cycle efficiency

Value-added time divided by total lead time, expressed as a percentage. It quantifies how much of the process duration actually adds value for the customer.

Poka-yoke

Error-proofing: a design or device that prevents a mistake from being made or makes it immediately obvious, eliminating defects at the source rather than detecting them later.

5S

Workplace organization method with five steps: Sort, Set in order, Shine, Standardize, and Sustain. It reduces search time and motion waste while making abnormal conditions visible.

Kaizen

Continuous incremental improvement involving the people who do the work. Kaizen events are short, focused workshops that implement changes quickly and standardize the results.

Control plan

A document specifying the controls applied to each significant process or product characteristic, including monitoring method, sample frequency, and the reaction plan when out of control.

Corrective action

Action taken to eliminate the root cause of a detected nonconformity so it does not recur. It is distinct from containment, which addresses the immediate symptom.