BACKGROUND Random errors in measurement of a risk factor will introduce downward bias of an estimated association to a disease or a disease marker. This phenomenon is called regression dilution bias. A bias correction may be made with data from a validity study or a reliability study. AIMS AND METHODS In this article we give a non-technical description of designs of reliability studies with e...

A pilot study asks whether something can be done, should the researchers proceed with it, and if so, how. However, a pilot study also has a specific design feature; it is conducted on a smaller scale than the main or full-scale study. In other words, the pilot study is important for improvement of the quality and efficiency of the main study. In addition, it is conducted in order to assess the ...

Sample-size determination is often an important step in planning a statistical study—and it is usually a difficult one. Among the important hurdles to be surpassed, one must obtain an estimate of one or more error variances, and specify an effect size of importance. There is the temptation to take some shortcuts. This paper offers some suggestions for successful and meaningful sample-size deter...

OBJECTIVE To assess the average age of menarche in Pakistani girls from different socioeconomic backgrounds. METHODOLOGY This was a cross sectional study design carried out on female students studying in different schools of Karachi in 2014. Girls aged 10-14 years age were included. Schools from all three socio economic strata were selected through random sampling technique from a list of sch...

BACKGROUND AND OBJECTIVE The studies measured Out-of-Pocket Expenditure (OOPE) for hospital births previously suffer from serious data limitations. To overcome such limitations, we designed a hospital-based study for measuring the levels and factors of OOPE on maternity care for hospital births by its detailed components. METHODS Data were collected from women for non-complicated deliveries 2...

Sample size calculation formulas for testing equality, noninferiority, superiority, and equivalence based on odds ratio were derived under both parallel and one-arm crossover designs. An example concerning the study of odds ratio between a test compound (treatment) and a standard therapy (control) for prevention of relapse in subjects with schizophrenia and schizoaffective disorder is presented...

There have been few epidemiological surveys to establish prevalence and associated risk factors of psychosis in Sub-Saharan Africa. This paper reports a population-based epidemiological survey in rural Kenya of the prevalence of psychotic symptoms and their relationship with demographic, socio-economic and other risk factors. A random sample of 2% of all adults living in Maseno, Kisumu District...

We consider a model of evolution in games in which a revising agent observes the actions of a random number of randomly sampled opponents and then chooses a best response to the distribution of actions in the sample. We provide a condition on the distribution of sample sizes under which an iterated p-dominant equilibrium is almost globally asymptotically stable under these dynamics. We show und...

BACKGROUND Previous reviews have focussed on the rationale for employing the stepped wedge design (SWD), the areas of research to which the design has been applied and the general characteristics of the design. However these did not focus on the statistical methods nor addressed the appropriateness of sample size methods used.This was a review of the literature of the statistical methodology us...