The limits of compliance can be inferred by the parametric method if the normality of the differences is indicated. or the use of non-parametric percentiles, if these assumptions are not included. The boundaries of agreement estimate the interval between some of the differences between the measures. For example, if you have a new method of measuring blood pressure, you can say that this is interchangeable with the method you are using now if the systolic and diastolic measurements performed simultaneously are within 10 mm Hg. You would appreciate the limits of the chord and, if the limits were closer to 10 mm Hg, you could say that the two methods are interchangeable. I am often asked how I say the limits of concordance, if the two measurement methods correspond. What is a good deal and what would be bad? This page also shows the standard deviation (SD) of the differences between the two test methods (called SD bias) and the 95% chord limits, calculated as the average difference (Bias) plus or minus 1.96 times sD. Based on a normal distribution of differences and sufficient sample size, the sample average and the sample SD are fairly close to their population, 95% of the differences between the two test methods would likely be within the range described by the 95% agreement limits. Proximity to measurements is a clinical decision, not a statistic. The 10 mm Hg in my example would be decided by the researcher or doctor who wants to know, not by me. The limits of the agreement do not contain a general coefficient that allows us to say whether the measurement method agrees. They are measuring how narrow the agreement is and we have to say whether it is close enough for what we want. Especially for small sample sizes, the sample average and sample SD may not have values close to the actual population average and SD.

To account for this possible discrepancy, it is possible to calculate 95% of forecast tapes for the difference between the two assage methods. These 95% prediction bands are wider than the 95% chord limits (especially for small samples) and therefore provide a more accurate prediction of future differences between the two test methods. Prism does not calculate the prediction strips, but they can easily be calculated by hand with a formula on page 146 of a Giavarina assessment (1). Compliance limitations include both systematic errors (bias) and random errors (precision) and provide a useful measure for comparing likely differences between different results measured using two methods. If one method is a reference method, compliance limits can be used as a measure of the total error of a measurement method (Krouwer, 2002). Myles – Cui. Use of the Bland-Altman method to measure compliance with repeated measurements. BJA: British Journal of Anaesthesia, Volume 99, issue 3, 1 September 2007, pages 309-311, doi.org/10.1093/bja/aem214. Https://academic.oup.com/bja/article/99/3/309/355972 call on April 23, 2018 Keywords: Bland-Altman-Plot, agree, two measures – Where are the limits of the agreement? If it is broad (as clinically defined), the results are ambiguous.