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<p>Meta-analysis is a method of synthesizing results of different studies conducted to answer a specific question. Meta-analysis applications have been published in a wide range of disciplines including medicine, education, psychology and many others. However, for many years, only pair-wise and direct comparisons have been made using standard meta-analysis methods. It is only recently that network meta-analysis emerged enabling the comparison of multiple treatments based on estimates from different studies. With network meta-analysis, the relative efficacy (or safety) of a particular intervention versus competing interventions can be obtained even in the absence of head-to-head evidence via a common comparator.</p> <p>An increasing number of methodologies related to network meta-analysis, assessments of underlying assumptions, and strategies for presentation of results have been proposed by several researchers. But only few simulation studies have been done to investigate different characteristics of this emerging statistical method. Hierarchical Bayesian meta-analysis model is commonly used in network meta-analysis to estimate effect of each intervention relative to every other. This model facilitates the calculation of the rank probabilities of a set of alternative treatments. However, various factors can determine the performance of the model which needs to be considered before using results for decision.</p> <p>This project aimed to investigate how the Bayesian hierarchical model estimates the rank probability of the best overall most effective treatment (i.e., the treatment ranked first) under different scenarios for modelling a binary outcome. Different network geometries, numbers of studies per comparison, sets of probabilities of success for treatments and sample sizes were investigated in our simulation study for binary outcome.</p> <p>Our simulation study showed that the estimates of treatments under consideration can be affected by network structures. Similar geometries affect the estimate in similar ways. Unbalanced number of studies per comparison influenced estimates of treatments in the geometries we considered. When a superior treatment is involved in the network, the hierarchical Bayesian mixed treatment model correctly identified it regardless of network patterns, number of studies and individual study sample size.</p> / Master of Science (MSc)

Objective: A sizable body of literature has now examined posttraumatic stress (PTS) symptoms in youth in the aftermath of disaster. Meta-analysis is the preferred tool with which to inform funding decisions, service delivery, and public policy. Method: The present meta-analysis quantitatively synthesized this literature (k=96 studies; Total N = 74,154), summarizing the magnitude of overall associations between disasters and youth PTS, and identifying child, disaster, and study method factors associated with variations in the magnitude of these associations. Results: Despite variability across studies, disasters had a significant effect on youth PTS symptoms, falling in the small-to-medium range of magnitude. Aspects related to pre-existing child characteristics, the disaster and the child’s disaster exposure, and study methodology are significantly associated with variations in the magnitude of disaster effects on youth PTS symptoms. Specifically, female gender, higher death toll, closer proximity, personal loss, and perceived threat and distress at the time of the event were each associated with increased post-disaster PTS in youth. Regarding methodological factors, studies conducted within the first year postdisaster, studies that used established PTS measures, and studies that relied on childreport data identified a significant effect on youth PTS, whereas studies conducted after the first year, studies relying on non-established measures, and studies relying on parentreport data did not. Conclusion: In the aftermath of disasters, governmental funding agencies and private foundations provide substantial resources for child services following disasters. The present meta-analytic findings can help to inform optimal allocation of these resources and targeted intervention efforts, as well as the development and refinement of new interventions for youth suffering in the aftermath of disasters. / Psychology

The purpose of this study is to investigate the overall effectiveness of extensive reading, and whether learners' ages impact learning from extensive reading differently. The second purpose is to investigate whether the length of time that second language learners engaged in extensive reading influenced outcome measures, and if an effect is found, identify effective periods of time for learners to engage in extensive reading. Meta-analysis was used to investigate the trends shown by past empirical research, chart future research directions, and provide a means to create alternative hypotheses for future research. Two types of empirical studies were conducted: group contrasts of studies that included control groups and pre-post contrasts of studies that only include experimental groups. This meta-analysis included 34 studies that provided 43 unique effect sizes (22 effect sizes for group contrasts and 21 effect sizes for pre-post contrasts) and a total sample size of 3,942 participants. Students who received extensive reading instruction outperformed those who did not. The effect size was small for group contrasts (d = .46) and medium for pre-post contrasts (d = .71). Moderator variables for each contrast were examined to assess the impact of learners' ages and the length of instruction; however, all groups substantially overlapped with each other in terms of their confidence intervals, indicating no statistically significant difference among the groups. There was a small effect size for university students for the group contrast (d = .48), a medium effect for high school students (d = .61), a large effect for university students (d = 1.12), and a large effect for adults (d = 1.48) for pre-post contrasts. In terms of the length of instruction, both one semester of instruction (d = .36) and one year of instruction (d = .52) produced a small effect for group contrasts, while one year of instruction produced a medium effect (d = .74) for pre-post contrasts. In sum, the available extensive reading research to date suggests that extensive reading improves students' reading proficiency and should therefore be a part of foreign language reading curricula. &#8195; / CITE/Language Arts

Among those seeking treatment for a substance use disorder (SUD), the prevalence of a concurrent anxiety disorder or posttraumatic stress disorder (PTSD) is surprisingly high, with some estimates placing the comorbidity rate at 33% to 43%. There is evidence that this comorbidity is associated with greater symptom severity, impairment, and substance use relapse than when the disorders present independently. One of the greatest challenges that clinicians face when presented with a patient with an anxiety disorder/PTSD and SUD is deciding how to approach treatment. Though the prevailing approach has been to treat the disorders sequentially, with the SUD receiving initial attention, there is a movement towards developing integrated or concurrent treatment models. The current meta-analytic study examined integrated or concurrent psychotherapies or pharmacotherapies for SUDs and anxiety disorders or PTSD. A meta-analysis on this topic is particularly important given the generally mixed findings of existing randomized controlled trials in this area of research. Our main question of interest was how integrated/concurrent treatments compared to single-target treatments. In addition, we explored whether there were outcome differences between psychotherapy and pharmacotherapy, between anxiety disorders and PTSD, and differences based on treatment setting (e.g., substance use treatment center versus other settings). Our findings suggested that integrated or concurrent treatments were superior in reducing anxiety or PTSD symptoms, compared to treatments that only targeted substance use or anxiety/PTSD. The effect, however, was small. There was no evidence that integrated or concurrent treatments improved substance use outcomes in comparison to stand alone substance use treatment. We also found evidence that treatment studies conducted at substance use inpatient or outpatient programs produced smaller anxiety/PTSD effects. A trend was found suggesting combined psychotherapy-pharmacotherapy interventions may be more effective than psychotherapy alone. No difference was found between treatments targeting PTSD versus anxiety disorders. Implications of our findings are discussed. / Psychology