CEN/TR 16886:2016

In the masonry unit standards and in national legislation, some properties need to be declared based on a certain fractile and confidence level. To demonstrate compliance with that a statistical tool can be used.
The purpose of this Technical Report is to exemplify how a statistical tool can be used in practice. This document should not contradict nor extend the scope of the work and role of a Notified Body, nor impose additional burdens on the manufacturer, beyond those laid down in the Construction Products Regulation and the product standards.
Mechanical and other properties of building materials and components are in the report described by random variables with a certain type of probability distribution. The popular normal distribution (Laplace-Gauss distribution) is given in Annex A. Normal distribution may be used to approximate many actual symmetrical distributions. When a remarkable asymmetry is observed, then another type of distribution reflecting this asymmetry should be considered, leading to a more complex method to demonstrate compliance with the product standard. More information on the normality test of Shapiro-Wilk is given in Annex D.