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Journal of Educational Evaluation For... 2021Appropriate sample size calculation and power analysis have become major issues in research and publication processes. However, the complexity and difficulty of... (Review)
Review
Appropriate sample size calculation and power analysis have become major issues in research and publication processes. However, the complexity and difficulty of calculating sample size and power require broad statistical knowledge, there is a shortage of personnel with programming skills, and commercial programs are often too expensive to use in practice. The review article aimed to explain the basic concepts of sample size calculation and power analysis; the process of sample estimation; and how to calculate sample size using G*Power software (latest ver. 3.1.9.7; Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany) with 5 statistical examples. The null and alternative hypothesis, effect size, power, alpha, type I error, and type II error should be described when calculating the sample size or power. G*Power is recommended for sample size and power calculations for various statistical methods (F, t, χ2, Z, and exact tests), because it is easy to use and free. The process of sample estimation consists of establishing research goals and hypotheses, choosing appropriate statistical tests, choosing one of 5 possible power analysis methods, inputting the required variables for analysis, and selecting the “calculate” button. The G*Power software supports sample size and power calculation for various statistical methods (F, t, χ2, z, and exact tests). This software is helpful for researchers to estimate the sample size and to conduct power analysis.
Topics: Humans; Research Design; Sample Size; Software
PubMed: 34325496
DOI: 10.3352/jeehp.2021.18.17 -
Nephron. Clinical Practice 2011The sample size is the number of patients or other experimental units that need to be included in a study to answer the research question. Pre-study calculation of the... (Review)
Review
The sample size is the number of patients or other experimental units that need to be included in a study to answer the research question. Pre-study calculation of the sample size is important; if a sample size is too small, one will not be able to detect an effect, while a sample that is too large may be a waste of time and money. Methods to calculate the sample size are explained in statistical textbooks, but because there are many different formulas available, it can be difficult for investigators to decide which method to use. Moreover, these calculations are prone to errors, because small changes in the selected parameters can lead to large differences in the sample size. This paper explains the basic principles of sample size calculations and demonstrates how to perform such a calculation for a simple study design.
Topics: Clinical Trials as Topic; Humans; Mathematical Concepts; Research Design; Sample Size
PubMed: 21293154
DOI: 10.1159/000322830 -
Indian Pediatrics Apr 2022Systematic reviews involve the application of scientific methods to reduce bias in review of literature. The key components of a systematic review are a well-defined... (Meta-Analysis)
Meta-Analysis
Systematic reviews involve the application of scientific methods to reduce bias in review of literature. The key components of a systematic review are a well-defined research question, comprehensive literature search to identify all studies that potentially address the question, systematic assembly of the studies that answer the question, critical appraisal of the methodological quality of the included studies, data extraction and analysis (with and without statistics), and considerations towards applicability of the evidence generated in a systematic review. These key features can be remembered as six 'A'; Ask, Access, Assimilate, Appraise, Analyze and Apply. Meta-analysis is a statistical tool that provides pooled estimates of effect from the data extracted from individual studies in the systematic review. The graphical output of meta-analysis is a forest plot which provides information on individual studies and the pooled effect. Systematic reviews of literature can be undertaken for all types of questions, and all types of study designs. This article highlights the key features of systematic reviews, and is designed to help readers understand and interpret them. It can also help to serve as a beginner's guide for both users and producers of systematic reviews and to appreciate some of the methodological issues.
Topics: Humans; Meta-Analysis as Topic; Research Design; Systematic Reviews as Topic
PubMed: 34183469
DOI: 10.1007/s13312-022-2500-y -
The New England Journal of Medicine Aug 2016Uncontrolled pilot studies have suggested the efficacy of focused ultrasound thalamotomy with magnetic resonance imaging (MRI) guidance for the treatment of essential... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Uncontrolled pilot studies have suggested the efficacy of focused ultrasound thalamotomy with magnetic resonance imaging (MRI) guidance for the treatment of essential tremor.
METHODS
We enrolled patients with moderate-to-severe essential tremor that had not responded to at least two trials of medical therapy and randomly assigned them in a 3:1 ratio to undergo unilateral focused ultrasound thalamotomy or a sham procedure. The Clinical Rating Scale for Tremor and the Quality of Life in Essential Tremor Questionnaire were administered at baseline and at 1, 3, 6, and 12 months. Tremor assessments were videotaped and rated by an independent group of neurologists who were unaware of the treatment assignments. The primary outcome was the between-group difference in the change from baseline to 3 months in hand tremor, rated on a 32-point scale (with higher scores indicating more severe tremor). After 3 months, patients in the sham-procedure group could cross over to active treatment (the open-label extension cohort).
RESULTS
Seventy-six patients were included in the analysis. Hand-tremor scores improved more after focused ultrasound thalamotomy (from 18.1 points at baseline to 9.6 at 3 months) than after the sham procedure (from 16.0 to 15.8 points); the between-group difference in the mean change was 8.3 points (95% confidence interval [CI], 5.9 to 10.7; P<0.001). The improvement in the thalamotomy group was maintained at 12 months (change from baseline, 7.2 points; 95% CI, 6.1 to 8.3). Secondary outcome measures assessing disability and quality of life also improved with active treatment (the blinded thalamotomy cohort)as compared with the sham procedure (P<0.001 for both comparisons). Adverse events in the thalamotomy group included gait disturbance in 36% of patients and paresthesias or numbness in 38%; these adverse events persisted at 12 months in 9% and 14% of patients, respectively.
CONCLUSIONS
MRI-guided focused ultrasound thalamotomy reduced hand tremor in patients with essential tremor. Side effects included sensory and gait disturbances. (Funded by InSightec and others; ClinicalTrials.gov number, NCT01827904.).
Topics: Activities of Daily Living; Aged; Double-Blind Method; Essential Tremor; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Postoperative Complications; Quality of Life; Thalamus; Ultrasonic Therapy; Ultrasonography, Interventional
PubMed: 27557301
DOI: 10.1056/NEJMoa1600159 -
Statistics in Medicine Jan 2021Meta-analyses of a treatment's effect compared with a control frequently calculate the meta-effect from standardized mean differences (SMDs). SMDs are usually estimated... (Meta-Analysis)
Meta-Analysis
Meta-analyses of a treatment's effect compared with a control frequently calculate the meta-effect from standardized mean differences (SMDs). SMDs are usually estimated by Cohen's d or Hedges' g. Cohen's d divides the difference between sample means of a continuous response by the pooled standard deviation, but is subject to nonnegligible bias for small sample sizes. Hedges' g removes this bias with a correction factor. The current literature (including meta-analysis books and software packages) is confusingly inconsistent about methods for synthesizing SMDs, potentially making reproducibility a problem. Using conventional methods, the variance estimate of SMD is associated with the point estimate of SMD, so Hedges' g is not guaranteed to be unbiased in meta-analyses. This article comprehensively reviews and evaluates available methods for synthesizing SMDs. Their performance is compared using extensive simulation studies and analyses of actual datasets. We find that because of the intrinsic association between point estimates and standard errors, the usual version of Hedges' g can result in more biased meta-estimation than Cohen's d. We recommend using average-adjusted variance estimators to obtain an unbiased meta-estimate, and the Hartung-Knapp-Sidik-Jonkman method for accurate estimation of its confidence interval.
Topics: Computer Simulation; Humans; Reproducibility of Results; Research Design; Sample Size
PubMed: 33180373
DOI: 10.1002/sim.8781 -
Epidemiology and Health 2019The objective of this study is to describe the general approaches to network meta-analysis that are available for quantitative data synthesis using R software. We...
The objective of this study is to describe the general approaches to network meta-analysis that are available for quantitative data synthesis using R software. We conducted a network meta-analysis using two approaches: Bayesian and frequentist methods. The corresponding R packages were "gemtc" for the Bayesian approach and "netmeta" for the frequentist approach. In estimating a network meta-analysis model using a Bayesian framework, the "rjags" package is a common tool. "rjags" implements Markov chain Monte Carlo simulation with a graphical output. The estimated overall effect sizes, test for heterogeneity, moderator effects, and publication bias were reported using R software. The authors focus on two flexible models, Bayesian and frequentist, to determine overall effect sizes in network meta-analysis. This study focused on the practical methods of network meta-analysis rather than theoretical concepts, making the material easy to understand for Korean researchers who did not major in statistics. The authors hope that this study will help many Korean researchers to perform network meta-analyses and conduct related research more easily with R software.
Topics: Humans; Meta-Analysis as Topic; Research Design; Software
PubMed: 30999733
DOI: 10.4178/epih.e2019013 -
Northern Clinics of Istanbul 2021Cholecystectomy is the standard treatment of acute cholecystitis. Surgery, however, poses significant risks for patients with advanced age and/or comorbid conditions.... (Review)
Review
Cholecystectomy is the standard treatment of acute cholecystitis. Surgery, however, poses significant risks for patients with advanced age and/or comorbid conditions. For such patients, percutaneous cholecystostomy (PC) is the only option. This interventional procedure does not have any absolute contraindications because of the life-threatening nature of the disease, in which other treatment options cannot be offered due to their risks. Nonetheless, these risk factors necessitate performing PC under urgent, rapid, and in many cases suboptimal conditions. In this article, PC was revisited in the light of our extensive experience in addition to the most current literature. Pre-procedural evaluation including the risk assessment and procedural steps was presented in detail. If conducted properly, PC provides significant clinical improvement in the short term and is life-saving, especially in the elderly and in patients with comorbid diseases or high surgical risk. It may also be the definitive treatment method for acute cholecystitis.
PubMed: 34909596
DOI: 10.14744/nci.2021.81594 -
BMJ Open May 2019Pharmacotherapy plays an important role in the treatment of major depression. At the initiation of antidepressant treatment, both improvement of symptoms in the short...
INTRODUCTION
Pharmacotherapy plays an important role in the treatment of major depression. At the initiation of antidepressant treatment, both improvement of symptoms in the short term and relapse prevention in the long term should be taken into account. However, there is insufficient evidence regarding the efficacy and the acceptability of continuation/maintenance treatments and the relative efficacy/acceptability of antidepressants.
OBJECTIVE
We will conduct a pairwise meta-analysis and a network meta-analysis (NMA) to examine the relative efficacy, tolerability and acceptability of antidepressants in the long-term treatment of major depression.
METHODS AND ANALYSIS
We will include double-blind randomised controlled trials comparing any of the following antidepressants, which we included in our previous NMA of the acute treatment for major depression, with placebo or with another active drug for long-term treatment of major depression: agomelatine, amitriptyline, bupropion, citalopram, clomipramine, desvenlafaxine, duloxetine, escitalopram, fluoxetine, fluvoxamine, levomilnacipran, milnacipran, mirtazapine, nefazodone, paroxetine, reboxetine, sertraline, trazodone, venlafaxine, vilazodone and vortioxetine. Our primary outcomes will be sustained response and all-cause dropouts. We will include four types of designs that are used to investigate long-term treatment. We will conduct two main analyses. First, we will conduct a pairwise meta-analysis comparing all antidepressants versus placebo to investigate whether continuing antidepressants after achieving a positive response in the acute-phase treatment is beneficial and/or safe. Second, we will conduct an NMA to examine the comparative efficacy and acceptability of the drugs. We will use a novel approach that will combine the results of acute-phase treatment NMA with long-term treatment studies to include all related designs in the NMA. We will ensure the validity of combining different designs and our new approach by checking the distribution of important effect modifiers and consistency of network.
ETHICS AND DISSEMINATION
This study did not require ethical approval. We will disseminate our findings by publishing results in a peer-reviewed journal.
PROSPERO REGISTRATION NUMBER
CRD42018114561; Pre-results.
Topics: Humans; Antidepressive Agents; Depressive Disorder, Major; Meta-Analysis as Topic; Research Design; Systematic Reviews as Topic; Network Meta-Analysis
PubMed: 31110100
DOI: 10.1136/bmjopen-2018-027574 -
European Urology Focus Sep 2023Network meta-analysis (NMA) expands upon traditional meta-analysis by integrating three or more interventions. This allows comparing interventions using evidence from... (Review)
Review
Network meta-analysis (NMA) expands upon traditional meta-analysis by integrating three or more interventions. This allows comparing interventions using evidence from trials that have compared pairs of interventions directly, and indirect evidence through common comparators. We provide an overview of NMA concepts and considerations when interpreting results from a systematic review with a NMA and applying them to clinical practice. PATIENT SUMMARY: Network meta-analysis is a statistical tool that allows researchers to compare multiple treatments for a medical condition at once, even when treatments have not been compared to each other in research studies. This mini-review explains how to read a network meta-analysis and apply its results in patient care.
Topics: Network Meta-Analysis; Systematic Reviews as Topic; Meta-Analysis as Topic
PubMed: 37925328
DOI: 10.1016/j.euf.2023.10.018