Important research questions are typically studied and analyzed more than once, often by different research teams in different locations. However, in many instances, the results of these multiple small studies are diverse and conflicting, which makes decision-making difficult. The need to arrive at decisions fostered the momentum towards synthesizing the results of these multiple studies. Therefore, meta-analysis, also referred to as the standard or traditional meta-analysis, is a statistical technique for combining the results or findings from multiple independent studies to address a specific research question. The applications of meta-analysis have been extended to many fields of research including medicine, psychology, ecology, education, business and many others. Prior to carrying out a meta-analysis or statistically synthesizing data, a researcher must undertake a systematic review. Systematic review attempts to collate empirical evidence that fits pre-specified eligibility criteria to answer a specific research question. That is to determine which studies will be included or excluded from the analysis. Standard meta-analysis methods are used to obtain the relative efficacy (or safety) of a particular intervention versus a competing intervention in the presence of a direct or head-to-head comparison. Thus only a pair-wise comparison can be made. The outcome of these interventions could be continuous, binary or count data. A number of methodologies related to meta-analysis, assessments of underlying assumptions and strategies for the presentation of results have been proposed by several researchers. A commonly used model for estimating effect sizes in meta-analysis is the fixed-effect model. However, various factors can determine the performance of the model which needs to be considered before using the results for decision making. This project aimed to investigate the performance of hypothesis properties and estimation properties on selecting data points from an underlying contaminated distribution under different scenarios for modeling a continuous outcome. Different levels of contamination, levels of significance, number of studies, number of individual study sample sizes, standard deviations and effect sizes were investigated in our simulation study for a continuous outcome. The results of our simulation study shows that, the fixed-effect meta-analytic model does not perform well in the presence of contamination. As the level of contamination in the treatment group increases, the properties of estimators and hypothesis are greatly influenced. The method performs well as expected in the absence of contamination but performs poorly as we observe 50% contamination in the treatment group regardless of the individual sample size, the number of studies, the standard deviation and the effect size. / Thesis / Master of Science (MSc)

Syfte: Föreliggande litteraturstudie syftar till att utvärdera den parodontala hälsan hos patienter som har haft en adhesivt cementerad retentionstråd under en period av minst fem år efter att ha genomgått ortodontisk behandling.   Material och metod: Litteratursökning gjordes systematiskt med hjälp av PICO och PRISMA med väldefinierade inklusions- och exklusionskriterier. Tre sökdatabaser användes, PubMed/MEDLINE, Scopus och Web of Science. Endast studier som uppfyllde kriterierna efter granskningsprocessen inkluderades och resultatet bearbetades efter bedömning av risk av bias via granskningsmall från Statens beredning för medicinsk och social utvärdering.   Resultat: Efter litteratursökning och granskning av potentiellt relevanta studier från de tre databaserna, identifierades endast två studier som uppfyllde alla urvalskriterier. En av de inkluderade studierna undersökte parodontal hälsa hos 211 patienter som genomgått ortodontisk behandling med fast apparatur. Patienterna hade fast retentionstråd på de sex anteriora tänderna lingualt i mer än sex år. Den andra studien som inkluderades omfattade 60 patienter som delades in i två grupper där en patientgrupp hade retentionstråd i 20 år och en kontrollgrupp. Den parodontala hälsan utvärderades i båda studierna med hjälp av olika parametrarna: plackindex, sonderingsdjup, gingivalretraktion, gingivalindex, tändernas placering och tandsten. Trots skillnader i använda utvärderingsverktyg presenterade båda studierna liknande resultat. Det fanns inte någon påverkan av retentionstrådens användning på den parodontala hälsan.   Slutsats: Adhesivt cementerad retentionstråd har inte någon signifikant effekt på den parodontala hälsan, men kan innebära en viss ökad risk för plack- och tandstensbildning hos patienterna.   Nyckelord: Ortodontisk retentionstråd, adhesivt cementerad retentionstråd, långsiktiga effekter, parodontal hälsa, gingival hälsa. / Purpose: This systematic literature study aims to investigate the longterm effect of adhesively cemented retainers on the periodontal health in patients who have undergone orthodontic treatment for at least five years. Materials and methods: Studies were systematically searched using PICO and PRISMA with well-defined inclusion and exclusion criteria, using three databases, i.e., PubMed/MEDLINE, Scopus, and Web of Science. Studies that met the criteria after the review-process were included and results were processed after assessing risk of bias according to a review template from Swedish Agency for Health Technology Assessment and Assessment of Social Services. Results: After searching and assessing potentially relevant studies from the three databases, only two studies were identified that met the selected criteria. One study examined periodontal health in 211 patients who underwent orthodontic treatment with fixed appliances. The patients had fixed retainers on the six anterior teeth lingually for more than six years. The second study consisted of 60 patients divided into two groups, one patient group with retainers for over 20 years and a control group. Different assessment tools were used in both studies: plaque-index, probing-depth, gingival recession, gingival-index, irregularity-index, and calculus. Despite the differences in assessment tools, both studies presented similar results, i.e., fixed retainers did not affect the periodontal health. Conclusion: Fixed retainers do not have a significant effect on periodontal health but may increase the risk of plaque and calculus formation in patients.

No description available.

No description available.

Like any other company, life insurance companies maintain a combination of debt and equity for their long-term financing, which forms their capital structure. Many theories have been developed in the literature to focus upon the determinants that are likely to affect leverage decisions of the life insurance firms in the post life Risk-Based Capital (RBC) regulation era. This report documents the application of multiple regression techniques to derive and analyze a Capital Asset Ratio (CAP) model based on the data pertaining to a large number of life insurance companies during 2000 to 2004. The data set is organized as panel data. Model coefficients, together with the error structure, are analyzed using SAS software to develop a valid model that tries to explain the Capital to Asset Ratio (CAP) for life insurers in terms of various variables of interest. The latter include return on capital, total assets, and two measures of risk: asset risk and product risk, etc. A balanced panel dataset was extracted from the given unbalanced input dataset containing missing entries. In addition, a selected few of the explanatory variables were chosen from a large group present in the input dataset based on previous work on relations among asset risk, product risk and capital in the life insurance industry by Etti G. Baranoff and Thomas W. Sager (2002). Fixed Effects model was chosen based on the assumption that the firm-specific effects were correlated to the explanatory variables. Differencing method was employed so that OLS estimator could safely be used for the coefficients in the regression model. Based on the proposed model, it is found that Capital to Asset Ratio has positive relationships with product risk and return on capital, with the corporate form of organization, and with membership in an affiliated group of companies. On the other hand, it has a negative relationship with company’s size and the ratio of life premiums or annuity premiums to the total premiums generated. / text

No description available.

No description available.

No description available.

No description available.

No description available.