Tag Archive | Control Charts

Types of Control Charts

The quality of a product or process may be assessed by means of

  • Variables : actual values measured on a continuous scale e.g. length, weight, strength, resistance, etc
  • Attributes : discrete data that come from classifying units (accept/reject) or from counting the number of defects on a unit

If the quality characteristic is measurable

  • monitor its mean value and variability (range or standard deviation)

If the quality characteristic is not measurable

  • monitor the fraction (or number) of defectives
  • monitor the number of defects

Defectives vs Defects
Defective or Nonconforming Unit

  • a unit of product that does not satisfy one or more of the specifications for the product

–e.g. a scratched media, a cracked casing, a failed PCBA

Defect or Nonconformity

  • a specific point at which a specification is not satisfied

–e.g. a scratch, a crack, a defective IC

Shewhart Control Charts – Overview

Shewhart Control Charts - Overview

Shewhart Control Charts – Overview

Shewhart Control Charts for Variables

Shewhart Control Charts for Variables

Shewhart Control Charts for Variables