Fig. 5

Probability density function and cumulative probability function for the Q₂ variable. Example of PDF and CPF for Q₂ for n =  12. The black dashed horizontal lines intersect the CPF at the two points of coordinates (L, 0.025) and (U, 0.975), while the red dashed horizontal lines intersect the CPF at the two points of coordinates (L^1st, 0.25) and (U^3rd, 0.75), where L^1st and U^3rd identify the first and third quartile, respectively. As a consequence, the black and red arrows mark the intervals of the variable Q₂ corresponding to a statistical significance of 95% and 50%, respectively