Mazzuco and Scarpa [ 5] have introduced a different model based on skew-normal density function which has 4 parameters.
In strategy 2, these 14 nodes are modeled using a skew-normal distribution with the mode of the distribution near the minimum bound and the tail extending into the past.
In the next section, we show that the skew-logistic model as a new fertility model has 4 parameters, just as the skew-normal model.
In this paper, we introduce skew-logistic probability density function as a better model: its residuals are less than those of the skew-normal model and it can more precisely estimate the parameters of the model.
This model is less useful for unimodal age-specific fertility rate patterns, so a model based on skew-symmetric (skew-normal) pdf was proposed by Mazzuco and Scarpa (2011) which was flexible for unimodal and bimodal fertility patterns.
This model is fitted to the age-specific fertility rate data, and it has been shown that the residuals of this model are less than the residuals of the skew-normal model.
Outputs of this program show that, with the same data, the norm of the residual (resnorm) of the skew-normal model is 148.7917 and the resnorm of the skew-logistic model is 143.5909.
As it is shown in [ 5] and Figure 2, which is for an Italian data set, the skew-normal model is generally a better fit, with lower residuals.
In these figures, the residuals of the skew-normal model are somewhat less than those of the other models.
Recently, Mazzuco and Scarpa (2011) [ 5] proposed a model based on generalization of the skew-normal distribution (FGSN).
