ISO/WD TS 10928-2

Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Methods for regression analysis and their use — Part 2: Non-linear method ISO/WD TS 10928-2

Scope

Within the hypothetical context of a model for a set of data obtained from a long-term stiffness test on GRP test pieces, the objective of this document is to produce explicit formulae for:
a) estimating all four parameters in the model, i.e. a, b, c and d, and
b) calculating confidence and prediction intervals about the curve.
These formulae are presented in this annex, along with associated graphical displays for a typical data set.
NOTE While the data and procedures refer to a long-term stiffness test, the method can also be applied to data which fit the mathematical model and require extrapolation to 50 years.