![]() It is normal for samples to pass through a 4 step sequential analysis after receipt in the laboratory: 1. In these patterns, the two appendages are mirror images of each other, with morphological characteristics at their junctions with the rest of the atriums on both sides of either right type or left type. Instead, there is isomerism of the atrial appendages. The two other arrangements do not show such lateralisation. In these two arrangements, the appendages are lateralised, with the morphologically right appendage being to one side, and the morphologically left appendage to the other. It is often called situs inversus, even though the atrial chambers are not upside down. The second arrangement, very rare, is the mirror image of the usual. The most common is the usual arrangement, also called situs solitus, in which the morphologically right appendage is right-sided, and the morphologically left appendage is left-sided. When arrangement of the atriums is assessed according to the morphology of the junction of the appendages with the rest of the atriums, 19 then since all hearts have two atrial appendages, each of which can only be of morphologically right or left type, there are only four possible patterns of arrangement ( Fig. The cornerstone of any system of sequential analysis must be accurate establishment of atrial arrangement, since this is the starting point for subsequent analysis. Anderson, in Paediatric Cardiology (Third Edition), 2010 ATRIAL ARRANGEMENT For instance, we can obtain a final structure like this, each star indicating a significant relation between periods: However, on the basis of successive statistical tests, it is then possible to suppress one by one the nonsignificant relations, starting from the highest order relations, until reaching the simplest structure of association between the four periods being still statistically similar to the saturated model. This model is not really interesting by itself, since it does not reduce in any manner the complexity of the initial observed situation. The starting point of a log-linear analysis, the so-called saturated model, uses all possible relations between the four periods, to exactly reproduce the observed data. In addition to the single effect induced by the independent distribution of activities observed during each period, we can also consider the six possible two-way contingency tables computed between two different periods among four, the four possible tri-way contingency tables, and the unique four-way contingency table, using the four periods simultaneously. Consider for instance a situation where we would like to identify the possible relations between activities observed during four successive periods, from t to t + 3. A log-linear model is designed for the analysis of multiple-way contingency tables. It is also possible to reformulate a lag-sequential analysis in log-linear terms. When the researcher is more interested by this higher level of analysis, Agresti suggests that the log-linear approach should be preferred. The lag- sequential analysis focuses on the identification of particular patterns of successive activities, rather than on the global relation between all possible activities at different times.
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