To explore the relationship of the productivity performance, the analysis focuses on understanding which ones of
the indicators listed above are relevant factors of the number of stops of the drivers. This goal is reached through a
regression analysis that aims at testing if the independent variables considered are significant factors and whether
they have positive or negative impact on the response variable (Tuckey, 1977). First, the normality test on the
response variable has been performed, and then all the independent factors have been normalized, so that to get a
better comprehension of the results after the analysis. In order to have predictors linearly independent from one and
others the multicollinearity check has been performed (Tabanick and Fidell, 2001).
In order to evaluate the level of multicollinearity among independent variables, it can be used the Variance
Inflation Factor (VIF), calculated as follows: