TECHNOLOGY OVERVIEW

Variables Sampling Plan - Fraction Defectives - Standard Deviation Known

BIS.Net Team

Variables acceptance sampling plans are used when quality characteristics are measured on a continuous scale. Variables sampling plans tend to be more efficient than Attributes Sampling plans with a much lower sample size.

This type of sampling plan protects against the receipt, or release of lots with excessive defectives. Defectives are items where measurements fall outside specification limits. For example moisture content may be specified for a delivery of a raw material. If the percentage of moisture that falls outside specification limits is excessive the lot will be rejected. The proportion falling outside specification limits is called fraction defective. The percentage is called percent defectives, which is 100 times the fraction defectives.

This plan requires for you to specify the lower and upper specification limits, the AQL and LTPD, including the producer’s and consumer’s risks and known standard deviation.

The BIS.Net Acceptance Sampling Plan App provides an OC CURVE and the Sampling Plan for its output, such as shown below.

The purpose of the OC Curve is to assess the probabilities of acceptance and rejection at all levels of percentage defectives