Fig 7. Comparison of measured duration of hospital stay Dⁱⁿ and predicted the duration of of hospital stay ${\widehat{D}}^{\text{in}}$ by linear regression model with geometric mean of strength μ_G(s) and age as input variables.

(a) μ_G(s). (b) μ_G(s) and age. ${\widehat{D}}^{\text{in}}$ obtained by five-fold cross validation is shown. Both are underfitting and do not fully explain the variation in Dⁱⁿ.