● additional random effects, described as random-effect factors;
● specific effects from determinate sources, described as controlledor fixed-
effect factors.Where one additional effect may be present, a one-way ANOVAis used, whilst
for two additional effects, two-way ANOVA is appropriate. Both involve much
lengthier calculations than the simpler tests of significance, but facilities for
these are available with computer packages such as Microsoft Excel and
Minitab.
Typical examples of the use of ANOVA are:● analysis of a heterogeneous material where variation in composition is an
additional random factor;
● analysis of samples by several laboratories, methods or analysts where the
laboratories, methods or analysts are additional fixed-effect factors;
● analysis of a material stored under different conditions to investigate
stability where the storage conditions provide an additional fixed-effect
factor.40 Section B – Assessment of data