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Statistical issues – significantly important in medical research

Medical researchers may regard a study mostly as a project with medical methods and issues to be dealt with by medical professionals. Nevertheless, this view may allow input from other fields when necessary. For instance, a study often includes some statistical calculations, and if an easily handled program package is not available, there may be a need for a statistician. The belief that statistics is equal to analysis leads unfortunately to the phenomenon that statisticians are contacted at the end of the study period, when it is time for ‘mathematical acrobatics’. Unfortunately this is, in many cases, too late – not even the most sophisticated analyses could rescue errors made during the earlier vital steps, e.g. in the design and sample size calculation. As a consequence many publications in medical journals are statistically poor or even wrong (1–3), and many studies are not published due to statistical weakness. In short, medical researchers are often not aware of the importance and broad use of statistics in a study, even though it is clear that statistics has an important role in medical research. In 1983 it was shown that 70% of published articles in the New England Journal of Medicine used statistical analysis (4). Since then the use of statistics has increased and is nowadays more or less standard. In contrast to this view, a statistician may regard a clinical study more as a study based on statistical concepts with clinical input, rather than a clinical study with statistical input. From this point of view it can be rather frustrating not to be part of the vital planning and design questions which, in the opinion of a statistician – to a high degree – are considered as statistical matters. Statisticians can in many cases easily find statistical errors in studies, and sometimes are even annoyed by (or find enjoyable) the lack of statistical precision. Why these views differ and why there is a lack of cooperation is not discussed in this article. As a statistician I can only admit that statisticians have a great responsibility, especially with regard to marketing and presentation of theory in its entirety and in an understandable way. It is time to increase cooperation and to create a mutual point of view. Both medical researchers and statisticians must understand that each single step of a study needs both medical and statistical input to achieve high scientific quality. In this article some of the basic statistical concepts of a study are explained and justified. Design issues are discussed briefly while statistical significance is discussed in detail. The focus is on experimental confirmatory clinical trials on humans, but there are some comments regarding observational studies, e.g. case-control studies. The objective is to illustrate that statistical issues are important to all stages of a study. Furthermore, the intention is to give the reader an increased understanding of statistics, an interest in basic concepts, some good advice, and references to help produce high quality studies.