Statistical Quality Control glossary

z ≈ 1.645; a wider acceptable margin of error, a smaller required sample.

Taught in Sampling and collecting data

z ≈ 1.96; the most commonly used standard in quality work.

Taught in Sampling and collecting data

z ≈ 2.576; a narrower margin of error, requiring a larger sample.

Taught in Sampling and collecting data

How close a measurement is to the true value, a systematic property (bias).

Taught in Sampling and collecting data

Examining every single unit in the population, no sampling error, but far costlier.

Taught in Sampling and collecting data

The population is divided into clusters, and whole clusters are sampled.

Taught in Sampling and collecting data

Can take any value within a range, e.g. weight, dimension, temperature.

Taught in Sampling and collecting data

Units are selected for ease of access or the sampler's judgement, not randomly.

Taught in Sampling and collecting data

Countable, whole-number values only, e.g. number of defects per batch.

Taught in Sampling and collecting data

Errors from sources other than sampling itself, faulty measuring instruments, data entry mistakes, or a poorly worded questionnaire.

Taught in Sampling and collecting data

A numerical characteristic of the population (e.g. the true population mean).

Taught in Sampling and collecting data

The complete set of items or observations a study is interested in.

Taught in Sampling and collecting data

How close repeated measurements are to each other, regardless of whether they are close to the true value.

Taught in Sampling and collecting data

Describes a quality or category, e.g. defect type, colour grade.

Taught in Sampling and collecting data

Describes a measurable quantity, e.g. weight, length, count of defects.

Taught in Sampling and collecting data

A subset of the population actually observed or measured.

Taught in Sampling and collecting data

Examining a representative subset of the population.

Taught in Sampling and collecting data

The natural difference between a sample statistic and the true population parameter, purely because a sample, not the whole population, was observed.

Taught in Sampling and collecting data

Every unit has an equal chance of selection.

Taught in Sampling and collecting data

A numerical characteristic calculated from a sample, used to estimate a parameter.

Taught in Sampling and collecting data

The population is divided into groups (strata) and a sample is drawn from each.

Taught in Sampling and collecting data

Units are selected at a fixed interval from a randomly chosen start.

Taught in Sampling and collecting data

A characteristic that can take different values across the units observed.

Taught in Sampling and collecting data