The replication crisis hit the medical sciences about a decade ago, but today still most of the flaws inherent in null hypothesis significance testing (NHST) have not been solved. While the drawbacks ...of p-values have been detailed in endless venues, for clinical research, only a few attractive alternatives have been proposed to replace p-values and NHST. Bayesian methods are one of them, and they are gaining increasing attention in medical research, as some of their advantages include the description of model parameters in terms of probability, as well as the incorporation of prior information in contrast to the frequentist framework. While Bayesian methods are not the only remedy to the situation, there is an increasing agreement that they are an essential way to avoid common misconceptions and false interpretation of study results. The requirements necessary for applying Bayesian statistics have transitioned from detailed programming knowledge into simple point-and-click programs like JASP. Still, the multitude of Bayesian significance and effect measures which contrast the gold standard of significance in medical research, the p-value, causes a lack of agreement on which measure to report.
Therefore, in this paper, we conduct an extensive simulation study to compare common Bayesian significance and effect measures which can be obtained from a posterior distribution. In it, we analyse the behaviour of these measures for one of the most important statistical procedures in medical research and in particular clinical trials, the two-sample Student's (and Welch's) t-test.
The results show that some measures cannot state evidence for both the null and the alternative. While the different indices behave similarly regarding increasing sample size and noise, the prior modelling influences the obtained results and extreme priors allow for cherry-picking similar to p-hacking in the frequentist paradigm. The indices behave quite differently regarding their ability to control the type I error rates and regarding their ability to detect an existing effect.
Based on the results, two of the commonly used indices can be recommended for more widespread use in clinical and biomedical research, as they improve the type I error control compared to the classic two-sample t-test and enjoy multiple other desirable properties.
Inference in Experiments With Matched Pairs Bai, Yuehao; Romano, Joseph P.; Shaikh, Azeem M.
Journal of the American Statistical Association,
10/2022, Volume:
117, Issue:
540
Journal Article
Peer reviewed
Open access
This article studies inference for the average treatment effect in randomized controlled trials where treatment status is determined according to a "matched pairs" design. By a "matched pairs" ...design, we mean that units are sampled iid from the population of interest, paired according to observed, baseline covariates and finally, within each pair, one unit is selected at random for treatment. This type of design is used routinely throughout the sciences, but fundamental questions about its implications for inference about the average treatment effect remain. The main requirement underlying our analysis is that pairs are formed so that units within pairs are suitably "close" in terms of the baseline covariates, and we develop novel results to ensure that pairs are formed in a way that satisfies this condition. Under this assumption, we show that, for the problem of testing the null hypothesis that the average treatment effect equals a prespecified value in such settings, the commonly used two-sample t-test and "matched pairs" t-test are conservative in the sense that these tests have limiting rejection probability under the null hypothesis no greater than and typically strictly less than the nominal level. We show, however, that a simple adjustment to the standard errors of these tests leads to a test that is asymptotically exact in the sense that its limiting rejection probability under the null hypothesis equals the nominal level. We also study the behavior of randomization tests that arise naturally in these types of settings. When implemented appropriately, we show that this approach also leads to a test that is asymptotically exact in the sense described previously, but additionally has finite-sample rejection probability no greater than the nominal level for certain distributions satisfying the null hypothesis. A simulation study and empirical application confirm the practical relevance of our theoretical results.
The data presented herein represents the simulated datasets of a recently conducted larger study which investigated the behaviour of Bayesian indices of significance and effect size as alternatives ...to traditional p-values. The study considered the setting of Student's and Welch's two-sample t-test often used in medical research. It investigated the influence of the sample size, noise, the selected prior hyperparameters and the sensitivity to type I errors. The posterior indices used included the Bayes factor, the region of practical equivalence, the probability of direction, the MAP-based p-value and the e-value in the Full Bayesian Significance Test. The simulation study was conducted in the statistical programming language R.
The R script files for simulation of the datasets used in the study are presented in this article. These script files can both simulate the raw datasets and run the analyses. As researchers may be faced with different effect sizes, noise levels or priors in their domain than the ones studied in the original paper, the scripts extend the original results by allowing to recreate all analyses of interest in different contexts. Therefore, they should be relevant to other researchers.
Using the paired T-Test to compare suppliers De Brito, Caroline Soares; Silva, Dayana Elizabeth Werderits; Aguiar, Luiz Guilherme de Andrade ...
GeSec : Revista de Gestão e Secretariado,
10/2023, Volume:
14, Issue:
10
Journal Article
Peer reviewed
Open access
The manufacture of industrial products requires rigorous quality, which is why they need to be in compliance. It is therefore essential that two different suppliers present products within the same ...specifications. The aim of this article is to show a case study carried out in a company in the south of the state of Rio de Janeiro, which used the Paired T Test to compare two types of foam for hospital mattresses. The results showed that supplier 1 produces a foam below the specified thickness of 11 cm while supplier 2 produces a foam within the specified value, so supplier 1 would be rejected and supplier 2's service would be used.
With the broad deployment of Wi-Fi networks, the Received Signal Strength (RSS) based Wi-Fi indoor localization has attained much interest of both academia and industry. At present, most of the ...currently available Wi-Fi indoor localization techniques focus on increasing the localization accuracy. However, few of them take into account the diversity of Wi-Fi signal distributions and the measurement error associated with RSS values owing to the complicated indoor environment, which consequently results in the low robustness of indoor localization systems. Thus, with the motivation to tackle this gripping problem, we design a new hybrid hypothesis test based on the idea of Asymptotic Relative Efficiency (ARE), which exploits signal distributions by considering different Access Point (AP) contributions to the Wi-Fi indoor localization accuracy. In concrete terms, first of all, the Jarque-Bera (JB) test is used to perform the normality test on the Wi-Fi signal distribution at each Reference Point (RP), and then the Chi-squared Automatic Interaction Detection (CHAID) approach is applied to obtain each AP contribution degree. Secondly, based on the evaluation of the JB test on the Wi-Fi signal distribution, the hybrid Mann-Whitney U and T test is applied to find the set of matching RPs corresponding to each newly-collected RSS data. Finally, the target location estimate is acquired by using the K-Nearest Neighbor (KNN), where the contribution degree of each AP is assigned as the weight during the calculation to find matching RPs. From the extensive experimental results, it is evident that the proposed approach can successfully improve the system performance by achieving a higher localization accuracy and enhanced robustness when compared with the state-of-the-art Wi-Fi indoor localization techniques.
Patients who showed an inhibitory pattern at the first assessment had a continuous improvement in V-HIT performance, while patients with an initial excitatory response had a transient decrease in ...gain at the subsequent evaluation (P=.001). Hyperventilation, hyperventilation induced nystagmus, nystagmus, vertigo, vestibular neuritis, vestibulo-ocular reflex INTRODUCTION Hyperventilation-induced nystagmus test (HINT) is a procedure that can be easily performed during a bedside evaluation of dizzy patients without causing them excessive stress.1 It is well reported that the metabolic changes induced by hyperventilation can elicit a nystagmus in various vestibular disorders and that HINT can be used to reveal vestibular imbalance due to its ability to bring out asymmetries both at a central and a peripheral level.1-2-3 A unique feature of the HINT is its capability to generate a nystagmus in the absence of any dynamic stimulation of the labyrinth and, for this reason it has good sensitivity in cases of diseases that involve the central nervous system or the vestibular nerve.2-4-5-6 A positive test has been reported in 91.7% of cases of acoustic neuroma, in 75% of cases of multiple sclerosis, and in 72.7% of cerebellar diseases.5 Acute unilateral vestibular neuritis, also called acute unilateral vestibulopathy (AUVP), is one of the most common causes of vertigo. The excitatory response is less common; it can be observed almost exclusively during the acute phase, and it tends to be replaced by an inhibitory pattern during the follow-up.8The test seems to correlate with the severity of dizziness, but a clear prognostic value has not yet emerged.9 Aim of this study is to indicate the clinical role of HINT in AUVP, in particular the correlation between the evoked pattern and the gain of the vestibulo-ocular reflex (VOR) evaluated with the video head impulse test (V-HIT). All the patients fulfilled the criteria for acute unilateral vestibulopathy according to the Barany Society: presence of spontaneous unidirectional nystagmus, history of rotatory vertigo with an acute onset lasting more than 24 hours, positive clinical head impulse test (HIT), absence of hearing loss, and contralateral normal vestibular and cochlear function.7 In order to have a homogeneous group, we selected patients who showed signs of superior vestibular neuritis.
Glioblastoma multiforme (GBM) is the most malignant brain tumor with rapid angiogenesis. How to inhibit GBM angiogenesis is a key problem to be solved. To explore the targets of inhibiting GBM ...angiogenesis, this study confirmed that the expression of circMTA1 (hsa_circ_0033614) was significantly upregulated in human brain microvascular endothelial cells exposed to glioma cell‐conditioned medium (GECs). The expression of circMTA1 in the cytoplasm was significantly higher than that in the nucleus. Upregulated circMTA1 in GECs can promote cell proliferation, migration, and tube formation. Further exploration of the circularization mechanism of circMTA1 confirmed that KHDRBS1 protein can bind to the upstream and downstream flanking sequences of circMTA1 and promote circMTA1 biogenesis by coordinating Alu element pairing. KHDRBS1 upregulated the proliferation, migration, and tube formation of GECs by promoting the biogenesis of circMTA1. CircMTA1 can encode the protein MTA1‐134aa by internal ribosome entry site sequence‐mediated translation mechanism, and promote the proliferation, migration, and tube formation of GECs through the encoded MTA1‐134aa. This study provides a new target for inhibiting angiogenesis in brain GBM and a new strategy for improving the therapeutic efficacy of GBM.
To explore the targets of inhibiting glioblastoma multiforme (GBM) angiogenesis, this study confirmed that circMTA1 was upregulated in human brain microvascular endothelial cells exposed in glioma cell‐conditioned medium (GECs). Mechanistic studies showed that KHDRBS1 cooperates with Alu elements in flanking introns of circMTA1 to promote circularization. CircMTA1 could translate into a 134aa protein termed MTA1‐134aa in an IRES‐dependent manner. MTA1‐134aa promoted GECs proliferation, migration, and tube formation. This study provides a new target for inhibiting angiogenesis in brain GBM.
Summary
Despite being an area of cancer with highest worldwide incidence, oral cancer yet remains to be widely researched. Studies on computer‐aided analysis of pathological slides of oral cancer ...contribute a lot to the diagnosis and treatment of the disease. Some researches in this direction have been carried out on oral submucous fibrosis. In this work an approach for analysing abnormality based on textural features present in squamous cell carcinoma histological slides have been considered. Histogram and grey‐level co‐occurrence matrix approaches for extraction of textural features from biopsy images with normal and malignant cells are used here. Further, we have used linear support vector machine classifier for automated diagnosis of the oral cancer, which gives 100% accuracy.
Lay description
Despite being an area of cancer with highest worldwide incidence, oral cancer yet remains to be widely researched. Studies on computer‐aided analysis of pathological slides of oral cancer contribute a lot to the diagnosis and treatment of the disease. Some researches in this direction have been carried out on oral submucous fibrosis. In this work an approach for analysing abnormality based on textural features present in squamous cell carcinoma histological slides have been considered. Histogram and grey‐level co‐occurrence Matrix approaches for extraction of textural features from biopsy images with normal and malignant cells are used here. Further, we have used linear support vector machine classifier for automated diagnosis of the oral cancer, which gives 100% accuracy.
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