Statistical Analysis for Studies of Intraocular Lens Formula Accuracy

[...]a cubic root transformation gives the same weight to a change in prediction error from 0.00 diopter (D) to 0.10 D as from 0.10 D to 0.60 D. The preferred method to statistically analyze absolute errors is nonparametric tests. If the P value is statistically significant, post hoc analysis can be carried out to find out which group or groups are responsible for the null hypothesis being rejected, to correct for the multiple comparisons made.