Parameters of significance in the
prediction were selected by stepwise variable
selection. This approach is a systemic method for
adding and removing terms from a multi-linear
model, based on their statistical significance in a
regression, beginning with fitting an initial model
and then comparing the explanatory power of
incrementally larger and smaller models. At each
step, the p-value of an F-statistic is computed to
test models with and without a potential term. If a
term is not currently in the model, the null
hypothesis is that the term would have a zero
coefficient if added to the model. If there is
sufficient evidence to reject the null hypothesis,
the term is added to the model. Conversely, if a
term is currently in the model, the null hypothesis
is that the term has a zero coefficient. If there is
insufficient evidence to reject the null hypothesis,
the term is removed from the model. However,
once a variable is in the equation, it may be