Variable Sampling Plans ISO 3951 for Textile Properties
topic
ISO 3951 variable sampling plans test smaller samples than equivalent attribute plans by using measurement data mean and standard deviation to estimate the fraction of lot outside specification, requiring measurements to follow a normal distribution; form k and form s plans use different acceptability criteria depending on whether process standard deviation is known or estimated from the sample.
Role
Reduces inspection sample size requirements for measured textile properties including yarn count, fabric weight, breaking strength, and colour coordinates compared to attribute sampling, providing greater statistical efficiency when the underlying distribution of the measured property can be assumed to follow a normal distribution from process knowledge.