0000000000427317
AUTHOR
Jean-baptist Du Prel
Critical Appraisal of Scientific Articles
Despite the increasing number of scientific publications, many physicians find themselves with less and less time to read what others have written. Selection, reading, and critical appraisal of publications is, however, necessary to stay up to date in one’s field. This is also demanded by the precepts of evidence-based medicine (1, 2). Besides the medical content of a publication, its interpretation and evaluation also require understanding of the statistical methodology. Sadly, not even in science are all terms always used correctly. The word "significance," for example, has been overused because significant (or positive) results are easier to get published (3, 4). The aim of this article …
Assessing vaccine efficacy for the prevention of acute otitis media by pneumococcal vaccination in children: a methodological overview of statistical practice in randomized controlled clinical trials.
Acute otitis media (AOM) is the most common bacterial infectious disease among children. Vaccination is proposed to prevent otitis and several clinical trials were performed to assess the efficacy of pneumococcal vaccines. The way vaccine efficacy is analysed varies among trials. However, the clinical meaning of an estimate of vaccine effect and its statistical test depends on the applied statistical method. We aim to bring the meaning and validity of statistical trial results to the attention of researchers. We consider all methodological approaches for analysing vaccine efficacy applied in pneumococcal vaccination trials included in a recent Cochrane Review. We demonstrate how different m…
Study Design in Medical Research
Medical research studies can be split into five phases—planning, performance, documentation, analysis, and publication (1, 2). Aside from financial, organizational, logistical and personnel questions, scientific study design is the most important aspect of study planning. The significance of study design for subsequent quality, the relability of the conclusions, and the ability to publish a study are often underestimated (1). Long before the volunteers are recruited, the study design has set the points for fulfilling the study objectives. In contrast to errors in the statistical evaluation, errors in design cannot be corrected after the study has been completed. This is why the study design…
Evaluation of a new pooling strategy based on leukocyte count for rapid quantification of allele frequencies.
Abstract Background: Allele frequencies of single-nucleotide polymorphisms (SNPs) can be quantified from DNA pools. The conventional preparation of DNA pools requires DNA isolation and quantification for each blood sample. We hypothesized that pooling of whole blood samples according to their leukocyte count, which determines DNA content, would be as reliable as the conventional pooling method but much less tedious to perform. Methods: We collected 100 whole blood samples and measured the leukocyte count. Samples were frozen until further use. After thawing, pools were generated by combining aliquots containing an equal number of leukocytes. In parallel, DNA was extracted from another aliqu…
Confidence Interval or P-Value?: Part 4 of a Series on Evaluation of Scientific Publications
An understanding of p-values and confidence intervals is necessary for the evaluation of scientific articles. This article will inform the reader of the meaning and interpretation of these two statistical concepts.The uses of these two statistical concepts and the differences between them are discussed on the basis of a selective literature search concerning the methods employed in scientific articles.P-values in scientific studies are used to determine whether a null hypothesis formulated before the performance of the study is to be accepted or rejected. In exploratory studies, p-values enable the recognition of any statistically noteworthy findings. Confidence intervals provide informatio…
Descriptive Statistics
A set of medical data is based on a collection of the data of individual cases or objects, also called observation units or statistical units. Every case, for example every study participant, patient, every experimental animal, every tooth or every cell shows comparable parameters (such as body weight, gender, erosion, pH). Each of these parameters, also called variables, has a specific parameter value (gender = male, age = 30 years, weight = 70 kg) for each observation unit (for example the patient). The aim of descriptive statistics is to summarize the data, so that they can be clearly illustrated (1–3). The property of a parameter is specified by its so-called scale of measure. Generally…
Avoiding Bias in Observational Studies
Background Many questions in human health research can only be answered with observational studies. In contrast to controlled experiments or well-planned, experimental randomized clinical trials, observational studies are subject to a number of potential problems that may bias their results.