Bland-Altman plots are widely used to assess the agreement between two instruments or two measurement techniques. Bland-Altman plots identify systematic differences between measures (i.e. fixed pre-stress) or potential outliers. The average difference is the estimated distortion, and the SD of the differences measures random fluctuations around this average. If the average value of the difference based on a 1-sample-t test deviates significantly from 0, this means the presence of a solid distortion. If there is a consistent distortion, it can be adjusted by subtracting the average difference from the new method. It is customary to calculate compliance limits of 95% for each comparison (average difference ± 1.96 standard deviation of the difference), which tells us how much the measurements were more likely in two methods for most people. If the differences in the average± 1.96 SD are not clinically important, the two methods can be interchangeable. The 95% agreement limits can be unreliable estimates of population parameters, especially for small sampling sizes, so it is important to calculate confidence intervals for 95% compliance limits when comparing methods or evaluating repeatability. This can be done by the approximate Bland and Altman method [3] or by more precise methods. [6] Previous work in this context is a formal agreement between the organizations concerned, in which both internal and external parties can participate.

In the case of a contract with external parties, it may be a „real“ contract, but also a Memorandum of Understanding (LoI), a Memorandum of Understanding (MOU), an „authorization to prosecute“ (ATP) or a „declaration of work“ (SOW). LoI, MoU and ATP are precursors to a contract and already settle certain cases, especially in the legal field between the parties where liability is also covered. Without a formal contract or contract, a great (legal) risk is possible and should be avoided! As a project manager, ask to what extent it is possible to charge the external client with a loI, moU or ATP (this may not be possible). If a SoW is used, it should be possible to charge an external customer. Bland and Altman indicate that two measurement methods developed to measure the same parameter (or property) should have a good correlation when a group of samples is selected so that the property to be determined varies considerably. Therefore, a high correlation for two methods of measuring the same property could in itself be only a sign that a widely used sample has been chosen. A high correlation does not necessarily mean that there is a good agreement between the two methods. A Bland-Altman plot (differential diagram) in analytical chemistry or biomedicine is a method of data representation used in the analysis of the agreement between two different trials.

It is identical to a tube of average difference Tukey,[1] the name under which it is known in other areas, but it was popularized in the medical statistics of J. Martin Bland and Douglas G. Altman. [2] [3] Some of these problems are due to a lack of adequate transparency and oversight of contracts. During the negotiation process, you are disadvantaged by immediate access to your contract library because you cannot see prior agreements to get an idea of a fair offer. Google is excused by the implementation of this agreement to the extent that performance is prevented, delayed or hindered by causes beyond its proper control.

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