A large body of research dating back to the 19th century has shown evidence for consistent relationships between ecological variables across geographical space (Lomolino et al., 2006; Gaston et al., 2008). These so-called ecogeographical ‘rules’ are often observed both within and among species and across lineages. Here we focus on three of the most familiar Department of Biology, University of ...

A good estimate of the design effect is critical for calculating the most efficient sample size for cluster surveys. We reviewed the design effects for seven nutrition and health outcomes from nine population-based cluster surveys conducted in emergency settings. Most of the design effects for outcomes in children, and one-half of the design effects for crude mortality, were below two. A reasse...

PURPOSE This pilot study examines the effects of walking a labyrinth. METHOD A convenience sample of 25 community members participated in a four-group, repeated measures study to gather information about vital signs and affect before and after labyrinth walks. Because of the small sample size, results were inspected for effect size (ES) differences in pre-to postcomparisons. Mean postwalk sco...

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...

In the present article, we investigate predictors of how often a scientific article is cited. Specifically, we focus on the influence of two often neglected predictors of citation rate: effect size and sample size, using samples from two psychological topical areas. Both can be considered as indicators of the importance of an article and post hoc (or observed) statistical power, and should, esp...

BACKGROUND Cluster-randomized trials, in which health interventions are allocated randomly to intact clusters or communities rather than to individual subjects, are increasingly being used to evaluate disease control strategies both in industrialized and in developing countries. Sample size computations for such trials need to take into account between-cluster variation, but field epidemiologis...

In bird species where males incubate but are smaller than females, egg size may be constrained by male body size, and hence ability to incubate the eggs. Using data from 71 such shorebird species, we show that egg size decreases as the degree of female-biased sexual size dimorphism increases, after controlling for female body mass. Relative egg size was not related to mean clutch size. However,...

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 an epidemiological study. There are several approaches to determining sample size. It depends on the type of the study. Descriptive, observational and randomized controlled studies have different formulas to calculate sample size. In this article, we discuss the formulas that can help to estimate sample size in an epidemiological ...

An appropriate sample size is crucial for the success of many studies that involve a large number of comparisons. Sample size formulas for testing multiple hypotheses are provided in this paper. They can be used to determine the sample sizes required to provide adequate power while controlling familywise error rate or false discovery rate, to derive the growth rate of sample size with respect t...