The accuracy describes how close to the actual or real value the measurement is, whereas the precision describes how close the values of repeated measurements are. Precision is related to how close repeated shots are to each other.How can we use these concepts when looking at the Bland-Altman plot?To investigate (1) the accuracy of the palpatory method to identify anatomical points by comparison with the X-ray exams, (2) the validity of classifying spinal posture in the frontal plane using Digital Image-Based Postural Assessment (DIPA) software by comparison with the X-ray exams and (3) the intra and inter-evaluator reproducibility of the DIPA software.
If the bias then is low, it means that the accuracy is high.
Limits of agreement refer to how precise the measurements are.
Bland-Altman analysis is used for assessing agreement between two measurements of the same clinical variable.
In the field of cardiac output monitoring, its results, in terms of bias and limits of agreement, are often difficult to interpret, leading clinicians to use a cutoff of 30% in the percentage error in order to decide whether a new technique may be considered a good alternative.
This percentage error of ± 30% arises from the assumption that the commonly used reference technique, intermittent thermodilution, has a precision of ± 20% or less.