Background When trials are subject to departures from randomised treatment, simple statistical methods that aim to estimate treatment efficacy, such as per protocol or as treated analyses, typically introduce selection bias. More appropriate methods to adjust for departure from randomised treatment are rarely employed, primarily due to their complexity and unfamiliarity. We demonstrate the use ...

A major challenge in the development of anticancer therapies is the considerable time and resources needed for conducting randomized clinical trials (RCT). There is a need for more efficient RCT designs that accelerate development, minimize costs, and make trials more appealing to patients. We review the statistical and logistical characteristics of multi-arm designs that compare several experi...

In cluster-randomized trials, intervention effects are often formulated by specifying marginal models, fitting them under a working independence assumption, and using robust variance estimates to address the association in the responses within clusters. We develop sample size criteria within this framework, with analyses based on semiparametric Cox regression models fitted with event times subj...

BACKGROUND Multi-item questionnaires are important instruments for monitoring health in epidemiological longitudinal studies. Mostly sum-scores are used as a summary measure for these multi-item questionnaires. The objective of this study was to show the negative impact of using sum-score based longitudinal data analysis instead of Item Response Theory (IRT)-based plausible values. METHODS In...

BACKGROUND A number of papers have proposed or evaluated the delayed-start design as an alternative to the standard two-arm parallel group randomized clinical trial (RCT) design in the field of rare disease. However the discussion is felt to lack a sufficient degree of consideration devoted to the true virtues of the delayed start design and the implications either in terms of required sample-s...

Spatial normalization is an essential process for group comparisons in functional MRI studies. In practice, there is a risk of normalization errors particularly in studies involving children, seniors or diseased populations and in regions with high individual variation. One way to minimize normalization errors is to create a study-specific template based on a large sample size. However, studies...

objective: the aim of this report was to study the gender role on autismsymptoms distribution and severity in a clinical sample from iran. then, the results were compared with the published study from the same community population sample, iran. method: the subjects of this retrospective study were a convenient clinical sample of the referrals of children with pervasive developmental disorders. ...