Table 2.

Correlation coefficient and root mean square error (RMSE) for the linear model (Eq. (5)) relating the measured refractive index to the relative density for the three different powders.

Material	$R^2$	RMSE
Lactohale 100	0.982	0.002
Lactohale 200	0.996	0.003
Lactohale 220	0.995	0.003