The Bland-Altman plot (Bland and Altman 1986) is often used in medical and chemical research to assess the consistency between two methods of measurement or testing (Giavarina 2015). McBride (2015) used the plot of Bland Altman in his simulation study on the impact of accuracy and accuracy on the ability to diagnose the adequacy of age estimation rates of fish. McBride (2015) found that Bland Altman`s plots «easily exhibit both bias and inaccuracy» and that this was summarized for «the entire sample and not for certain age groups.» Yet I know of only two entries in the fishing literature that used the Bland Altman conspiracy to compare the estimates of the switch (one in the grey literature, the other in a work). Afterwards, I describe the plot of Bland Altman, and then I offer a modified version to compare the estimates of the counter. Kappa ignores the degree of disagreement between observers and all differences are treated in the same way as complete disagreements. Therefore, if the categories are categorized, it is preferable to use Weighted Kappa (Cohen 1968) and assign different weights to subjects for which the raters differ, so that different levels of match can contribute to Kappa`s value. McBride, R.S. 2015. Diagnosis of the age agreement: a simulation of precision and precision effects. CIEM Journal of Marine Science 72:2149-2167. A weight vector of length 1 only means a strict match, each additional element increases the maximum number of disagree steps. If there are 5 categories, the linear sentence weights are 1, 0.75, 0.50, 0.25 and 0 if there is a difference of 0 (overall agreement) or 1, 2, 3 and 4 categories.

Overall square, weights are 1, 0.937, 0.750, 0.437 and 0. This article describes how to create a contract diagram in R. The Bland-Altman plot in Figure 1 was created with bland.altman.plot () from the BlandAltmanLeh package (Lehnert 2015b). Other R functions are available to create Bland-Altman plots (or the equivalent of Tukey`s average difference diagram). However, it is a simple diagram that can be easily constructed by «scratches,» as shown later. I then give a slight critique of the Bland-Altman plot for its use in age comparisons and offers an alternative (this is not a bias plot). Establishes a ranking table from raw data in the calculation table for two observers and calculates an inter-rater agreement statistic (Kappa) to assess the match between two classifications on ordinal or nominal scales. In this example, a Bland-Altman diagram is created to compare the age estimates of consensus (between two readers) (scaleC) and otolithC (otolithC) for Lake Champlain Lake Whitefish. Last week I posted a plot about a modified age bias.

In this post, I began to look more deeply at another action called Bland-Altman-Plot. Subsequently, I describe this action, show how to build it in R, I give a lenient critique of its use to compare the estimates of switches and I develop an alternative that means correcting what I consider to be some of the flaws in the use of the Bland-Altman plot to compare age estimates. It`s great a «think hard» exercise, so I`m open to any suggestions you may have.