scholarly journals Statistical Control Requires Causal Justification

2020 ◽  
Author(s):  
Anna Wysocki ◽  
Katherine M. Lawson ◽  
Mijke Rhemtulla

It is common practice in psychological research to use statistical control to remove the effect of third variables in correlational or quasi-experimental studies. Controlling for relevant confounders can improve estimates of the causal path from a predictor to the outcome, but this only works under ideal circumstances. When the selected control variables are inappropriate, controlling can result in regression coefficient estimates that are further from the causal path than uncontrolled estimates. Despite the ubiquity of control variables in published regression analyses and the consequences of controlling for inappropriate third variables, the selection of control variables is rarely well justified. We argue that to carefully select appropriate control variables researchers must propose and defend a causal structure that includes the outcome, predictors, and plausible confounders. Throughout, we underscore the importance of causality when selecting control variables by demonstrating via simulation the consequence of controlling for inappropriate variables. Finally, we provide practical recommendations for applied researchers who wish to use statistical control.

2020 ◽  
Vol 18 (3) ◽  
pp. 111-116
Author(s):  
Dulce Marieli Danieli ◽  
Fabíola De Almeida Gomes ◽  
Bruna Eibel ◽  
William Dhein

INTRODUÇÃO: O diafragma é o principal músculo respiratório e desempenha um papel importante na respiração e na regulação fisiológica. Uma terapia que visa melhorar essas condições referentes ao diafragma, é a técnica de liberação manual diafragmática. OBJETIVO: O objetivo deste estudo foi verificar a aplicabilidade clínica das técnicas manuais de liberação diafragmática e identificar as principais técnicas, populações investigadas, variáveis avaliadas e seus desfechos. MÉTODOS: Foram pesquisadas as seguintes bases de dados: PubMed, Scielo e Science Direct, com os descritores “Diaphragm [Mesh]” e “Musculoskeletal Manipulations [Mesh]” com seus correspondentes no mesmo idioma. Foram incluídos ensaios clínicos randomizados, não randomizados, estudos semi, quase-experimentais e estudos pilotos ou de caso, que abordaram técnicas de liberação manuais diafragmáticas.RESULTADOS: Há variadas técnicas de liberação diafragmática, sendo as mais mencionadas: normalização dos pilares do diafragma, alongamento e estiramento do diafragma, relaxamento dos pilares do diafragma. Além disso, as técnicas de liberação diafragmática vêm sendo associadas a protocolos de terapia manipulativa osteopática (TMO). As principais populações estudadas foram de pacientes saudáveis, com lombalgia, cervicalgia, osteoartrite, asmáticos, doença pulmonar obstrutiva crônica, constipados, cardiopatas e com refluxo gastroesofágico. Os principais desfechos avaliados são variáveis musculoesqueléticas (dor, flexibilidade, amplitude, espessura diafragmática), variáveis cardiorrespiratórias (pressão inspiratória/expiratória máxima (PImax e Pemax), mobilidade torácica, frequência cardíaca e respiratória), qualidade de vida e disfunções gastrointestinais/gastroesofágicas. CONCLUSÃO: A aplicabilidade clínica das técnicas de liberação diagramática está sendo investigada associado com outras técnicas osteopáticas, em protocolos de TMO em pacientes saudáveis, pneumopatas, cardiopatas, gestantes, em cicatriz pós-cirúrgica, constipados, com refluxo gastroesofágico, osteoartrite, cervicalgia e com lombalgia. Evidencia-se: diminuição ou eliminação das dores musculoesqueléticas, aumento da flexibilidade, ADM, Pimáx e Pemáx, aumento da mobilidade torácica, aumento da qualidade de vida, diminuição do inchaço e dor abdominal e sem efeito em cardiopatas.ABSTRACT. Clinical applicability of manual diaphragmatic release techniques: a systematic review.BACKGROUND: The diaphragm is the main respiratory muscle and plays an important role in breathing and physiological regulation. A therapy that aims to improve these conditions regarding the diaphragm, is the manual diaphragmatic release technique.OBJECTIVE: The aim of this study was to verify the clinical applicability of manual diaphragmatic release techniques and searching the main techniques, population, evaluated variables, and outcomes. METHODS: The following electronic databases were searched: PubMed, Scielo, and Science Direct, with the descriptors “Diaphragm [Mesh]” and “Musculoskeletal Manipulations [Mesh]” with their correspondents in the same language. There were included randomized clinical trial, non-randomized clinical trials, semi, and quasi-experimental studies, and pilot or case studies, which addressed manual diaphragmatic release techniques.RESULTS: There are various diaphragmatic release techniques, the most mentioned are: normalization of the diaphragm pillars, stretching of the diaphragm, relaxation of the diaphragm pillars, and protocols for osteopathic manipulative therapy (OMT) for the diaphragm. The main populations studied were healthy patients, with low back pain, asthmatics, chronic pulmonary obstructive disease, constipated, cardiac patients, and gastroesophageal reflux. The main outcomes assessed are musculoskeletal variables (pain, flexibility, range of motion, diaphragmatic thickness), cardiorespiratory variables (maximal inspiratory/expiratory pressure (MIP and MEP), chest mobility, heart, and respiratory rate), quality of life, and gastrointestinal/ gastroesophageal disorders.CONCLUSION: The clinical applicability of diagrammatic release techniques is being investigated in association with other osteopathic techniques, in protocols of OMT in healthy subjects, patients with lung diseases, heart disease, pregnant women, scar tissue, constipated, with gastroesophageal reflux, osteoarthritis, cervicalgia and with low back pain. There is evidence of reduction and elimination of musculoskeletal pain, increased MIP, increased chest mobility, an increase in health quality, a decrease of bloating and abdominal pain related to constipation, and a decrease of reflux symptoms.


Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 267
Author(s):  
Tomasz Rudnicki

The article presents a new functional method of designing self-compacting concrete (SCC). The assumptions of the functional method of designing self-compacting concrete were based on the double coating assumption (i.e., it was assumed that the grains of coarse aggregate were coated with a layer of cement mortar, whereas the grains of sand with cement paste). The proposed method is composed of four stages, each of which is responsible for the selection of a different component of the concrete mix. The proposed designing procedure takes into consideration such a selection of the mineral skeleton in terms of the volumetric saturation of the mineral skeleton, which prevents the blocking of aggregate grains, and the designed liquid phase demonstrated high structural viscosity and low yield stress. The performed experimental studies, the simulation of the elaborated mathematical model fully allowed for the verification of the theoretical assumptions that are the basis for the development of the method of designing self-compacting concrete.


2021 ◽  
Vol 13 (4) ◽  
pp. 2247 ◽  
Author(s):  
Ana Manzano-León ◽  
Pablo Camacho-Lazarraga ◽  
Miguel A. Guerrero ◽  
Laura Guerrero-Puerta ◽  
José M. Aguilar-Parra ◽  
...  

Educational gamification consists of the use of game elements and game design techniques in the educational context. The objective of this study is to examine the existing evidence on the impact of educational gamification on student motivation and academic performance in the last five years in order to analyze its distribution over time, educational level, variables, and most used game elements, and know the advantages of its implementation in the classroom. For this, a systematic review is proposed through the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) methodology in three multidisciplinary databases, through an exhaustive search with inclusion and exclusion criteria on quantitative experimental studies that explore gamification in educational centers, which provide information about the most current lines of research. Fourteen studies were included in this review. These used experimental or quasi-experimental designs. Most of them report gamification as a valid learning strategy. The results support the conclusion that educational gamification has a potential impact on the academic performance, commitment, and motivation of students. Therefore, this study implies the need to expand research on the needs and challenges of students when learning with gamified techniques.


Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3389
Author(s):  
Marcin Kamiński ◽  
Krzysztof Szabat

This paper presents issues related to the adaptive control of the drive system with an elastic clutch connecting the main motor and the load machine. Firstly, the problems and the main algorithms often implemented for the mentioned object are analyzed. Then, the control concept based on the RNN (recurrent neural network) for the drive system with the flexible coupling is thoroughly described. For this purpose, an adaptive model inspired by the Elman model is selected, which is related to internal feedback in the neural network. The indicated feature improves the processing of dynamic signals. During the design process, for the selection of constant coefficients of the controller, the PSO (particle swarm optimizer) is applied. Moreover, in order to obtain better dynamic properties and improve work in real conditions, one model based on the ADALINE (adaptive linear neuron) is introduced into the structure. Details of the algorithm used for the weights’ adaptation are presented (including stability analysis) to perform the shaft torque signal filtering. The effectiveness of the proposed approach is examined through simulation and experimental studies.


1985 ◽  
Vol 18 (4) ◽  
pp. 423-450 ◽  
Author(s):  
C. G. Kurland ◽  
Måns Ehrenberg

SUMMARYTheoretical as well as experimental studies of translational accuracy have most often been concerned with the selection of aminoacyl-tRNA by codon-programmed ribosomes. The selection of the successive codons on the mRNA has received much less attention, probably because it represents both conceptually and experimentally, a much more demanding physical problem. Nevertheless, it would seem that errors in the selection of the codon are potentially much more destructive than errors in selection of aminoacyl-tRNA species. This can be appreciated from the following.


Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1749
Author(s):  
Elzbieta Szychta ◽  
Leszek Szychta

Energy efficiency of systems of water pumping is a complex problem since efficiency of two distinct interacting systems needs to be combined: water and power supply. This paper introduces a non-intrusive method of calculating the so-called “collective losses” of a cage induction motor. The term “collective losses”, which the authors define, allows for accurate estimation of motor efficiency. Control system of a pump determines operating point of a pumping station, and thus its efficiency. General estimated performance characteristics of a motor, components of a control system, are assumed to serve selection of a range of pumping speed variations. Rotational speed has a direct effect on motor load torque, pump power and head, and thus on motor performance. Hellwig’s statistical method was used to specify characteristics of estimated collective losses on the basis of experimental studies of 21 motors rated at up to 2.2 kW. The results of simulations and experiments are used to verify validity and efficiency of the suggested method. The method is non-intrusive, simple to use, and requires minimum data.


2014 ◽  
Vol 7 (1) ◽  
pp. 36-67 ◽  
Author(s):  
YASUHIRO OZURU ◽  
DAVID BOWIE ◽  
GIULIA KAUFMAN

abstractThree quasi-experimental studies were conducted to investigate the relationship between the evaluative (i.e., agree/true) and the meta-cognitive (i.e., understand) response, and to determine which type of response people are more likely to provide when responding to one-sentence assertive statements. In Studies 1 and 2, participants performed two separate tasks in which they were asked to indicate the levels of: (i) understanding and (ii) agreement / perceived truthfulness of 126 one-sentence statements. The results indicated that participants were likely to provide a negative evaluative response (i.e., disagree/false) to a statement that they did not understand. In Study 3, participants were asked to evaluate the same 126 statements and choose between four response options: agree, disagree, understand, do not understand. The results indicated that people are more likely provide an evaluative response regardless of the understandability of a statement. The results of these studies are discussed in relation to (i) pragmatic perspective of how people infer speakers’ meaning, and (ii) cognitive processes underlying evaluative and meta-cognitive response.


2022 ◽  
Vol 14 (4) ◽  
pp. 82-89
Author(s):  
Sergey Polyakov ◽  
V. Akimov ◽  
A. Polukazakov

The article discusses the issues of implementing the conversion of input signals of «smart» sensors for automation of the heating system, an algorithm for calculating the parameters of measuring circuits with a nonlinear element and an operational amplifier is developed. The issues of modeling cascade control of residential building heating systems are investigated. The results of the analysis and selection of parameters of the cascade control system are presented. An algorithm implementing the operation of a virtual object is given. The structures of management of residential building objects are proposed. The method of calculating the adjustment of the controller for cascade control is given. For the heating system stand, the procedure for setting the parameters of the process of PID control of the coolant temperature is considered. The results confirming the achievability of the proposed structural changes are obtained. The results of experimental studies are presented.


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