Trial designs, including observational to interventional

2020 ◽  
pp. 57-64
Author(s):  
Edo Richard
Keyword(s):  
Study Design ◽  
Treatment Effect ◽  
Clinical Relevance ◽  
Observational Studies ◽  
Research Question ◽  
Sample Size Calculation ◽  
Target Population ◽  
Ethical Considerations ◽  
Neuropsychiatric Diseases ◽  
The Right

Observational studies have taught us a lot about the origin of neurological and neuropsychiatric diseases. This chapter describes how we can translate this knowledge into action. Before engaging in a large RCT, several steps have to be taken. First, the potential for a treatment effect has to be compelling. The target population in the RCT has to resemble the population in which observational studies described an association. Second, the outcome of an RCT has to be chosen, and has to have clinical relevance or at least have the potential of clinical relevance in the future. Third, the right study design has to be decided on. Each research question will require a specific study design with accompanying sample size calculation. Lastly, specific ethical considerations have to be taken into account when designing and executing an intervention study. This chapter presents an overview of these issues.

The most frequently asked question to a statistician: The sample size

2017 ◽  
Vol 23 (5) ◽  
pp. 644-646 ◽  
Author(s):  
Maria Pia Sormani
Keyword(s):  
Clinical Study ◽  
Sample Size ◽  
Study Design ◽  
Treatment Effect ◽  
Sample Size Calculation ◽  
Ethical Implications ◽  
Number Of Patients ◽  
Reducing Costs ◽  
Correct Size

The calculation of the sample size needed for a clinical study is the challenge most frequently put to statisticians, and it is one of the most relevant issues in the study design. The correct size of the study sample optimizes the number of patients needed to get the result, that is, to detect the minimum treatment effect that is clinically relevant. Minimizing the sample size of a study has the advantage of reducing costs, enhancing feasibility, and also has ethical implications. In this brief report, I will explore the main concepts on which the sample size calculation is based.

scholarly journals Design and Analysis of Observational Studies

2014 ◽  
Vol 5 (2) ◽  
pp. 33-39 ◽  
Author(s):  
KP Suresh ◽  
MR Gajendragad ◽  
H Rahman
Keyword(s):  
Observational Study ◽  
Study Design ◽  
Observational Studies ◽  
Research Question ◽  
Validity And Reliability ◽  
Current Review ◽  
Valid Result ◽  
Methods And Techniques ◽  
H Design

ABSTRACT Appropriate study design forms the basis of any successful organized research. Irrespective of the underlying rationale of the research question, inappropriate design of an experiment or execution of a study may not give a valid result. As defined, the research should have the following characteristics: it should be undertaken within the framework of a set of philosophies, should have an unbiased objective and a design comprising of methods and techniques that have been tested for their validity and reliability. These principles of research clearly emphasize the need for an appropriate study design. The current review focuses on the planning and analysis of an observational study to obtain significant and accurate findings. How to cite this article Suresh KP, Gajendragad MR, Rahman H. Design and Analysis of Observational Studies. Int J Infertil Fetal Med 2014;5(2):33-39.

scholarly journals Assessing risk of bias: a proposal for a unified framework for observational studies and randomized trials

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Hendrika J. Luijendijk ◽  
Matthew J. Page ◽  
Huibert Burger ◽  
Xander Koolman
Keyword(s):  
Study Design ◽  
Subject Matter ◽  
Health Care Professionals ◽  
Observational Studies ◽  
Randomized Trials ◽  
Outcome Measurement ◽  
Research Question ◽  
Subject Matter Knowledge ◽  
Unified Framework ◽  
Causal Diagrams

Abstract Background Evidence based medicine aims to integrate scientific evidence, clinical experience, and patient values and preferences. Individual health care professionals need to appraise the evidence from randomized trials and observational studies when guidelines are not yet available. To date, tools for assessment of bias and terminologies for bias are specific for each study design. Moreover, most tools appeal only to methodological knowledge to detect bias, not to subject matter knowledge, i.e. in-depth medical knowledge about a topic. We propose a unified framework that enables the coherent assessment of bias across designs. Methods Epidemiologists traditionally distinguish between three types of bias in observational studies: confounding, information bias, and selection bias. These biases result from a common cause, systematic error in the measurement or common effect of the intervention and outcome respectively. We applied this conceptual framework to randomized trials and show how it can be used to identify bias. The three sources of bias were illustrated with graphs that visually represent researchers’ assumptions about the relationships between the investigated variables (causal diagrams). Results Critical appraisal of evidence started with the definition of the research question in terms of the population of interest, the compared interventions and the main outcome. Next, we used causal diagrams to illustrate how each source of bias can lead to over- or underestimated treatment effects. Then, we discussed how randomization, blinded outcome measurement and intention-to-treat analysis minimize bias in trials. Finally, we identified study aspects that can only be appraised with subject matter knowledge, irrespective of study design. Conclusions The unified framework encompassed the three main sources of bias for the effect of an assigned intervention on an outcome. It facilitated the integration of methodological and subject matter knowledge in the assessment of bias. We hope that graphical diagrams will help clarify debate among professionals by reducing misunderstandings based on different terminology for bias.

scholarly journals Assessing Treatment Effect Variation in Observational Studies: Results from a Data Challenge

2019 ◽  
Vol 5 (2) ◽  
pp. 21-35
Author(s):  
Carlos Carvalho ◽  
Avi Feller ◽  
Jared Murray ◽  
Spencer Woody ◽  
David Yeager
Keyword(s):  
Treatment Effect ◽  
Observational Studies

Inference for treatment effect parameters in potentially misspecified high-dimensional models

Biometrika ◽  
2020 ◽  
Author(s):  
Oliver Dukes ◽  
Stijn Vansteelandt
Keyword(s):  
Sample Size ◽  
Confidence Intervals ◽  
Treatment Effect ◽  
Observational Studies ◽  
Treatment Effects ◽  
Treatment Selection ◽  
High Dimensional ◽  
Selection Mechanism ◽  
Dimensional Models ◽  
Effect Parameter

Summary Eliminating the effect of confounding in observational studies typically involves fitting a model for an outcome adjusted for covariates. When, as often, these covariates are high-dimensional, this necessitates the use of sparse estimators, such as the lasso, or other regularization approaches. Naïve use of such estimators yields confidence intervals for the conditional treatment effect parameter that are not uniformly valid. Moreover, as the number of covariates grows with the sample size, correctly specifying a model for the outcome is nontrivial. In this article we deal with both of these concerns simultaneously, obtaining confidence intervals for conditional treatment effects that are uniformly valid, regardless of whether the outcome model is correct. This is done by incorporating an additional model for the treatment selection mechanism. When both models are correctly specified, we can weaken the standard conditions on model sparsity. Our procedure extends to multivariate treatment effect parameters and complex longitudinal settings.

scholarly journals Generalizing Treatment Effect Estimates From Sample to Population: A Case Study in the Difficulties of Finding Sufficient Data

2016 ◽  
Vol 41 (4) ◽  
pp. 357-388 ◽  
Author(s):  
Elizabeth A. Stuart ◽  
Anna Rhodes
Keyword(s):  
Head Start ◽  
Randomized Trial ◽  
Treatment Effect ◽  
External Validity ◽  
Randomized Trials ◽  
Target Population ◽  
Data Sets ◽  
Common Data Elements ◽  
Ex Post

Background: Given increasing concerns about the relevance of research to policy and practice, there is growing interest in assessing and enhancing the external validity of randomized trials: determining how useful a given randomized trial is for informing a policy question for a specific target population. Objectives: This article highlights recent advances in assessing and enhancing external validity, with a focus on the data needed to make ex post statistical adjustments to enhance the applicability of experimental findings to populations potentially different from their study sample. Research design: We use a case study to illustrate how to generalize treatment effect estimates from a randomized trial sample to a target population, in particular comparing the sample of children in a randomized trial of a supplemental program for Head Start centers (the Research-Based, Developmentally Informed study) to the national population of children eligible for Head Start, as represented in the Head Start Impact Study. Results: For this case study, common data elements between the trial sample and population were limited, making reliable generalization from the trial sample to the population challenging. Conclusions: To answer important questions about external validity, more publicly available data are needed. In addition, future studies should make an effort to collect measures similar to those in other data sets. Measure comparability between population data sets and randomized trials that use samples of convenience will greatly enhance the range of research and policy relevant questions that can be answered.

Comparison of Bone-Conducted Vibration for Eliciting Ocular Vestibular-Evoked Myogenic Potentials

2011 ◽  
Vol 146 (2) ◽  
pp. 289-294 ◽  
Author(s):  
Chia-Chen Tseng ◽  
Shou-Jen Wang ◽  
Yi-Ho Young
Keyword(s):  
Prospective Study ◽  
Study Design ◽  
Healthy Subjects ◽  
University Hospital ◽  
Vestibular Evoked Myogenic Potentials ◽  
Ménière’S Disease ◽  
Asymmetry Ratio ◽  
Significant Difference ◽  
The Asymmetry ◽  
The Right

Objective. This study compared bone-conducted vibration (BCV) stimuli at forehead (Fz) and mastoid sites for eliciting ocular vestibular-evoked myogenic potentials (oVEMPs). Study Design. Prospective study. Setting. University hospital. Methods. Twenty healthy subjects underwent oVEMP testing via BCV stimuli at Fz and mastoid sites. Another 50 patients with unilateral Meniere’s disease also underwent oVEMP testing. Results. All healthy subjects showed clear oVEMPs via BCV stimulation regardless of the tapping sites. The right oVEMPs stimulated by tapping at the right mastoid had earlier nI and pI latencies and a larger nI-pI amplitude compared with those stimulated by tapping at the Fz and left mastoid. Similar trends were also observed in left oVEMPs. However, the asymmetry ratio did not differ significantly between the ipsilateral mastoid and Fz sites. Clinically, tapping at the Fz revealed absent oVEMPs in 28% of Meniere’s ears, which decreased to 16% when tapping at the ipsilesional (hydropic) mastoid site, exhibiting a significant difference. Conclusion. Tapping at the ipsilateral mastoid site elicits earlier oVEMP latencies and larger oVEMP amplitudes when compared with tapping at the Fz site. Thus, tapping at the Fz site is suggested to screen for the otolithic function, whereas tapping at the ipsilesional mastoid site is suitable for evaluating residual otolithic function.

Manifestations of legislative shortcomings in the Iraqi constitution

2021 ◽  
Author(s):  
Yamamah Kashkool ◽  
wael Al-bayati
Keyword(s):  
Prime Minister ◽  
Research Question ◽  
Economic Conditions ◽  
Research Questions ◽  
The Republic ◽  
The Right ◽  
Political Turmoil ◽  
Political Variables ◽  
Transitional Phase ◽  
New Phase

"The period of approving the Constitution of the Republic of Iraq for the year 2005 was surrounded by a state of political turmoil that usually accompanies any transitional phase that carries many political variables through the transition from a phase of dictatorial rule to a new phase bearing the features of democracy. In its approval, the lack of clarity in the political vision and the weakness of the constitutional legal culture of its authors, as well as the way in which it was approved by a popular referendum, which is voted on by yes or no, and does not allow an opportunity to discuss its articles and articles and diagnose its shortcomings. One of the shortcomings in our constitution is that it does not refer to regulating the resignation of the Prime Minister. This position has a political nature, and an administrative nature, and its occupant has the right to decide not to continue with this position and be satisfied with working in this field for any reason, and this must be in accordance with the context Organized legal, which is known as resignation., and this is what we dealt with in this research. For the purpose of researching this topic, we asked a research question that is... How can we address the legislative shortcomings that surrounded the Constitution of the Republic of Iraq for the year 2005 and related to regulating the resignation of the Prime Minister? From this research question, we derived several secondary research questions... 1- What is the limitation of legislative shortcomings? 2- What are the reasons for the legislative deficiencies in the Iraqi constitution? 3- Does the Prime Minister have the right to resign during his tenure? 4- To whom is the resignation submitted? 5- Who is the party that decides whether or not to accept the resignation? 6- What are the procedures that follow the acceptance of the resignation? By discussing these questions, we will try to reach the possibility of developing a legislative text that deals with a complete organization of the resignation of the Prime Minister, especially since the idea of ​​amending the constitution and to this day is still valid and possible, because many political, social and economic conditions in the country have changed from the time of entry into force of this constitution, which makes the idea of ​​the amendment obligatory and necessary"

scholarly journals Indonesia's Diplomacy in North Natuna Sea in Confronting China to Protect National Interests

FOCUS ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 21-27
Author(s):  
Gerald Theodorus Lumban Toruan ◽  
Adi Sunaryo
Keyword(s):  
Research Question ◽  
Secondary Data ◽  
Coast Guard ◽  
Regional Security ◽  
National Interests ◽  
The North ◽  
Fishing Vessels ◽  
Qualitative Descriptive ◽  
The Stability ◽  
The Right

North Natuna Sea is become a concern, at the end of 2019 to February 2020 this area was illegally entered by Chinese fishing vessels who wanted to fishing, this vessel was escorted by the Chinese Coast Guard. This escort is in order to protect their fishing vessels from the pursuit of Indonesian patrol vessels. According to the them that they did not violate Indonesian territory, they said that the North Natuna Sea still belongs to Chinese territory. In the perspective of the international relations what is done by China can disrupt the stability of regional security. This research is a qualitative descriptive with secondary data collection. The formulation of the research question is what kind of diplomacy is being carried out by Indonesia towards China in the North Natuna Sea. The purpose of this research is to find the right diplomacy concept in dealing with the China in the North Natuna Sea.

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