Because information regarding a large number of design variables was required for the knowledgebase,
the Design of Experiments (DoE) method was used. Design of Experiments is a formal method
of experimentation which allows the experimenter to obtain information about how independent factors
(variables) affect a given output, relative to each other [7]. Two-level designs involve the study of two
different values, also called levels, of each factor. Results of the DoE method include main effects,
two-level interaction effects, and higher level interaction effects. The main effect of one level of a
given factor is the effect of that factor’s value, averaged across all values of all other factors, on the
output. Interaction effects indicate how the output is affected by specific combinations of two or more
factor values, averaged across all combinations of all values of other factors. A positive effect
indicates that the output is, on average, increased when the factor (or set of factors) is at the specific
level(s) tested, while a negative effect indicates that the output is, on average, reduced by the tested
value or group of values.