Fig 5. Intra-individual agreement for heart rate indices.

For each HR index, Bland-Altman plots were used to assess intra-individual agreement. For each individual, the difference in each index between EST2 and EST1 (x2-x1) is plotted against the mean value (x₁+x₂)/2. Each subplot reports the bias, i.e. mean(x₂-x₁), the standard deviation of the differences, i.e. σ = std(x₂-x₁), the number of individuals outside the limits of agreements (%), and the total number of individuals. The confidence interval (bias ± 2σ, red lines) is reported in dashed lines.