In order to verify that this increase was not due to chance, we performed a Wilcoxon signed-rank test for related data based on next hypothesis. Experimental hypothesis : The improvement of skill level of students is statistically significant. Null hypothesis : the observed increase is due to chance. Results of Wilcoxon test revealed statistically significant differences in all the skills considered. Therefore we can reject the null hypothesis and assert that the increase in skill level is significant. To complement, sign test was also performed and results concluded that the compared variables (skills before and after) differ signif-icantly.