Quantitativeanalysisofpulmonarymeanlinear intercept (MLI), mean alveolarNumbers (MAN), pulmonary alveolar area (PAA) and the relative area of elasticfibers were measured.
Important cases where the computational definition of R2 can yield negative values, depending on the definition used, arise where the predictions which are being compared to the corresponding outcomes have not been derived from a model-fitting procedure using those data, and where linear regression is conducted without including an intercept.