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Published in Filomena Pereira-Maxwell, Medical Statistics, 2018
where 1.96 is the 2.5% percentage point of the standard Normal distribution. Note this is not a confidence interval, but rather an expression of the variability of observed disagreement. The calculation of the standard deviation (SD) of the differences is given under repeatability. A graphical display such as the Bland-Altman plot is a useful tool for evaluating both extent of agreement and presence of systematic features characterizing any existing disagreement, such as, for example, greater disagreement for higher or lower average values of the measurement in question. See BLAND (2015) and KIRKWOOD & STERNE (2003) for further details and illustrative examples. A related concept is that of reliability, measured (for quantitative variables) by the intraclass correlation coefficient (ICC) or by the index of reliability, R.
Instrument evaluation
Published in C M Langton, C F Njeh, The Physical Measurement of Bone, 2016
Christopher F Njeh, Didier Hans
The differences between methods (y axis) are likely to possess a normal distribution only if there is a random component to the error. The distribution of differences can be checked for normality by constructing a simple histogram (or by using a statistical package). A Bland-Altman plot should then be examined visually for any patterns that may exist in the differences of the two methods (figure 4.2). The possible relationship between the differences and the mean can be investigated formally by calculating the Spearman’s rank correlation coefficient (see section 4.4.3)
Machine learning models using non-linear techniques improve the prediction of resting energy expenditure in individuals receiving hemodialysis
Published in Annals of Medicine, 2023
Alainn Bailey, Mohamed Eltawil, Suril Gohel, Laura Byham-Gray
We used a modified Bland–Altman plot to measure the levels of agreement between mREE and eREE from each model [38]. The original Bland-Altman plot graphically assesses agreement between two methods of measurement by examining one method on the Y-axis by comparison with either the true measure on the X-axis or the mean of both measures if the criterion is not known [38]. In this case, we used residual values calculated via percentage on the Y-axis and mREE (the criterion measure) on the X-axis. A full description of the method was previously published by this group [27]. Limits of agreement for predictive equations have been established at ± 10% from zero difference from mREE in the nutrition literature [38]. Those limits have been used for validation by Byham-Gray et al. [21,23], Morrow et al. [25] and Bailey et al. [27] when assessing equations for people receiving dialysis [21,23,25,27]. This graphical analysis was applied to each of the best models (and the MHDE) across the complete validation sample for which REE was generated. The analysis was subsequently repeated with the validation set divided into subgroups of BMI. Individuals with a BMI less than 24.9 kg/m2, 25–29.9 kg/m2, or ≥ 30 kg/m2 were categorized as underweight/normal weight, overweight, or obese.
A new tool to measure occupational balance: Adolescent Occupational Balance Scale (A-OBS)
Published in Scandinavian Journal of Occupational Therapy, 2023
Güleser Güney Yılmaz, Hanife Avcı, Esra Akı
We found very strong correlational coefficients between the pre-test and posttest and concluded that the correlation between the two measurements was statistically significant. The reliability level of the scale was within the limits accepted as excellent. The Bland–Altman plot is a scatterplot in which the mean of the observations of the two measurements obtained is on the x-axis, and their differences are on the y-axis. If the differences are normally distributed, the differences are randomly distributed around 0 (or around a value close to zero) (in which case it is said that there is no relationship between the means and the differences), and 95% of them are bounded by 95, and the desired result between them is Figure 3). The results of the analyses showed that the reliability of the scale in the current study was strong.
Validation of Two Point of Care Devices for Hemoglobin Estimation in Blood Donors
Published in Hemoglobin, 2020
Deepika Chenna, Shamee Shastry, Kalyana-Chakravarthy Pentapati
Of the 100 samples, 95.0% were obtained from male donors. The mean ± SD of Hb measured using the reference method, CompoLab TM and True Hb (g/dL) were 14.79 ± 1.24, 15.15 ± 1.46 and 14.3 ± 1.76, respectively. The Bland–Altman plot, a graphical method to plot the difference scores of two measurements against the mean for each sample was plotted. Ninety-five percent of the data points were within ±1.96 SD of the mean difference, limits of agreement for a new device recording the measurements when compared to the standard. On average, CompoLab TM measured 0.4 units more than the reference method and True Hb measured 0.4 units less than the reference method (Figures 1 and 2). The value of two standard deviations of the difference of Hb measurement was >2.0 g/dL for both CompoLab TM and True HB.