# Agreement Sample Size

We can reach the upper confidence limit of the upper LOA limit and the lower confidence limit of the lower LOA limit, n being the sample size. In general, we place γ and α at 0.05. If the 95% confidence interval for the 95%-LOA is within the clinically acceptable and pre-defined agree limits, both methods are sufficiently suitable to meet the requirements of the agreement. In fact, the correspondence between confidence intervals for LOAs and hypothesis tests is the same here. Assuming that A is the lower limit and that B is the upper limit of the LOAs of population differences, we can construct the following simultaneous hypotheses: H01 is A δ, H12 is B ≤ δ. If the two null assumptions were rejected at the same time, both measures would be deducted from an agreement. The assumptions of the Bland-Altman method are similar to equivalence [13]. In this method, agreements (LoA) are calculated as the average value of differences between two measures ± 1.96 x of their standard deviation (Bland-Altman, 1986) 15. Zhou YH, Zang JJ, Wu MJ, Xu JF, He JF, He J. J Clin Lab Anal 2011;25:83-89. Based on the statistical principle of inference and mathematical theory of distribution, we deduced the sample size calculation formula for the Bland-Altman method under different parameter parameters. For simplicity`s sake, we provided a table that makes it easy to determine sample size for different standardized difference limits (μ/σ), standardized tuning limits (δ/σ) and type errors (β) under α-0.05.

The α and β should be considered large enough for sample size to have the half-width of a 100 (1x α) confidence interval less than a predefined width of 100 (1-β%). We have carried out monte-caro simulation studies to validate the accuracy of the proposed method. The results of the simulation show that the forces reached could correspond to the specified level of power, which validates the accuracy of the formulas. 6. Chhapola V, Kanwal SK, Brar R. Reporting Standards for Bland-Altman Agreement analysis in labor research: a cross-sectional survey of current practice. Ann Clin Biochem 2015;52:382-386. 1. Bland JM, DG Altman.

Statistical methods to assess the agreement between two methods of clinical measurement. Lancet 1986;i:307-310. The first important step in the Bland-Altman method is to draw the data and verify its model and distribution. The differences for both methods are presented against their means, and if the data behave well, then the construction of the different boundaries and the interpretation of the data are simple and simple. Assumptions about the limits of the agreement method are that differences resulting from two measures should have an approximate normal distribution, a constant variance of differences and proportional distortion [10]. There is proportional distortion when differences from average values increase or decrease [11]. 8. Bella ML, Teixeira-Pintoc A, McKenzied JE, Oliviere J. A variety of methods: The sample size calculated for two proportions depended on the choice of sample size formula and software. J Clin Epidemiol 2014;67:601-605.

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