Last mechanism of GAs is the elitism, which allows to clone the best chromosome of the previous generation and keep it unchanged for the next generation so to avoid a possible regression of the evolutionary process that might statistically occur: for example chromosome N.1 in Table 4 is the clone of the best chromosome in Table 1.
To avoid running a regression where information on the dependent variable (collected for the entire year) precedes the recording of the explanatory variables (collected in October), all explanatory variables in Eqs.
We did not include Architeuthis and Mesonychoteuthis in this part of the analysis in order to avoid a bias in the regression analysis.
Moreover, owing to the low number of events (deaths), we included only three variables in the multiple logistic regression analysis to avoid a final model of order slightly higher than required due to an overfitting effect [ 58].
Because of the limited absolute number of events (35 deaths) and in order to avoid an overparameterized model, Cox regression analysis, with a backward stepwise selection method to eliminate unnecessary control variables, was carried out to evaluate the effect of the biochemical and clinical variables for all-cause mortality, and hazard ratios (HR) were calculated.
Only three categorical variables were included in the multivariate Cox regression model to avoid an overfitting situation.
As the number of patients with VAP was 48, we only included seven variables in the regression analyses to avoid an over-fitting effect.
In fact, Fleming et al. (20) recently suggested that this approach is important to avoid any regression-to-the-mean effect and to provide the most unbiased estimates of effect.
The discrete nature of the residuals as respects time, generated by SEER's recording survival in months and not days, showed a minor reason to avoid Cox regression, which assumes data are not broadly grouped.
A cut-off of 0.40 for the P-value was chosen to avoid estimated regression coefficients being biased high (in absolute sense) and their standard errors being biased low.
