Sample size calculation is part of the early stages of conducting an epidemiological, clinical or laboratory study. In preparing a scientific paper, there are ethical and methodological indications for its use. Two investigations conducted with the same methodology and achieving equivalent results, but different only in terms of sample size, may point the researcher in different directions when...

A program of research begins with a good idea that materializes into a series of studies that carry the same theme. Each study builds upon the last, expanding on the findings to generate new questions, thus building the evidence base. The Center for Health Outcomes and Policy Research has built a 20-year program of research that has made great strides in establishing the evidence base that prof...

T trite but enduring cliché can be traced back to the late 19th century. The fact that it survived to this day indicates that perceptions of “success” can still differ widely between doctors and patients. For example, although the “1-yr graft patency” after coronary artery bypass surgery may be a highly meaningful outcome for a cardiac surgeon, it could have been achieved without any meaningful...

While the medical community has accepted the role of H. pylori in the pathogenesis of peptic ulcer disease, confusion persists among clinicians regarding when and on which patients to attempt H. pylori eradication. Thus, the objective for outcomes research in H. pylori is to help clinicians identify which patients benefit from H. pylori eradication and to determine the cost-effective strategies...

Is it better to have a heart attack in the United States or Canada? Ecological studies are epidemiological evaluations in which the unit of analysis is populations, or groups of people, rather than individuals.1 They can answer important questions such as the question posed above that cannot easily be answered using any other form of study design. Ecological studies are conducted by researchers...

Setting and participants. 3182 patients aged 18 to 65 years who had a body mass index (BMI) of 30 to 45 kg/m2 or BMI of 27 to 30 kg/m2 with at least 1 comorbid condition (hypertension, cardiovascular disease, dyslipidemia, impaired glucose tolerance, or sleep apnea). Exclusions included moderate or greater mitral regurgitation, mild or greater aortic regurgitation, diabetes, hypertension, pregn...

This article provides a brief overview of the individual differences approach to research. This approach is first compared with the more familiar group-based approach to research. Following this comparison, some of the procedural and statistical issues central to individual differences research are noted. Ultimately, individual differences research has the potential to be of the greatest benefi...