1
Data Reduction
Data for load carrying material properties can be modelled using any probability distribution function. Statistical goodness-of-fit tests should be
applied to determine if the data set could be randomly drawn from that
distribution. Modelling has progressed beyond a simple two parameter (/~,~)
Gaussian distribution. This book treats the three parameter (6,/~, 7) Weibull
distribution, as well as the traditional Gaussian distribution.
Many authors relegate the subject of data reduction to an appendix at
the back of the book. In the opinion of the authors, the topic deserves much
more attention.
I. REDUCTION OF RAW TABULATED TEST DATA OR
PUBLISHED BAR CHARTS
A computer program such as SAS (Statistical Analysis System) statistical
software or other compatible software is used to fit test data to a Gaussian
curve.
f(x) ~- ex p -
(1.1)
where -oo < x < + eo with
#-is the mean for an infinite sample size
J-is the standard deviation for an infinite sample size.
The program also fits data to a Weibull curve,
g(x)=/~[x-’]/~-’6
exp[ [x 7]’;
-~
(1.2)
whereT_ = 0whenx