Lege Artis Medicinae

[The medical application of Bayesian T-tests and traditional parametric T-tests]

MOLNÁR D. László1

APRIL 20, 2016

Lege Artis Medicinae - 2016;26(04)

[Bayesian statistical learning is a mixture of the hypothetico-deductive (“top down”) and inductive (“bottom up”) perspective of data analysis with a combination of prior distributions and the data using the Bayes theorem. The resulting posterior distributions are, in a figurative sense, similar to the middle part of a sand-clock. By analogy the upper part of this clock represents the hypothetico-deductive part in terms of prior distributions, while the lower part of that represents the inductive part in terms of the data. The prior distributions will then be continuously replaced with the posterior distributions in a learning cycle. The “top-down” and the “bottom up” methods are simultaneously used both in medicine and management sciences. On the other hand, traditional frequentist statistics can primarily be considered as an inductive method, which is mainly based on the data collected. Comparison of a scale variable measured in two groups is shown with the traditional parametric t-tests, nonparametric permutation test and various Bayesian t-tests. The corresponding R and WinBUGS codes are presented. ]


  1. Szociomed Kft.



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[INTRODUCTION - Myelofibrosis is a type of chronic myeloproliferative neoplasia frequently associated with extramedullary hematopoiesis. This latter process usually affects the spleen and the liver, and should be designated as nonhepatosplenic extramedullary hematopoiesis if it involves other organs. Nonhepatosplenic extramedullary hematopoiesis is reported to be more common in patients who had splenectomy. CASE REPORT - A 66-year-old woman with 5-year history of myelofibrosis was hospitalized eight month prior to death due to increasing abdominal effusion, abdominal discomfort and dyspnea. Three years before death, splenectomy was performed. The abdominal imaging studies disclosed a circumscribed tumorous mass in the pancreas, with enlargement of the peripancreatic lymph nodes. The lesion interpreted as pancreatic cancer progressed and the patient died. Post mortem histological evaluation confirmed the abdominal mass to represent myeloid metaplasia of the retroperitoneal fat tissue. CONCLUSIONS - Besides the possibility of a secondary primary tumor, the discovery of a novel mass lesion in patients with myelofibrosis should raise the suspicion of extramedullary hematopoiesis, especially when the patient had splenectomy.]

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[In an era where the number of medical liability suits is permanently increasing, it might be interesting - in Hungary as well -, and also useful to detect and analyse the roots of such liability in Continental/Euro­pean law. In classical Roman law - that also gives the basis for European ius commune - , we cannot encounter uniform and general norms governing medical liability. The reasons of such hiatus are inherent in the peculiar casuistic method of Roman law, as jurists focused on providing a proper solution for a specific case, and not on developing general and abstract behavioural norms. In addition to the foregoing, the legal status of physicians and their patients was heterogeneous: many doctors were foreign slaves who, if lucky, obtained freedom and Roman citizenship, or settled down in Rome as foreign citizens. The form of their professional liability was also determined by the legal status of their patients: if an untrained or careless physician tried to cure a slave owned by a Roman citizen and failed, the owner could sue the doctor for damaging his property. As far as free patients are concerned, we cannot formulate any unequivocal statements regarding medical liability and malpractice; however, the few available sources clearly prove that a physician who had wilfully caused harm to his free patient resulting in death was severely punished in ancient Rome.]

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