Category Epidemiology

The guard’s dilemma

Sensitivity and specificity The world of medicine is a world of uncertainty. We can never be sure of anything at 100%, however obvious it may seem a diagnosis, but we cannot beat right and left with ultramodern diagnostics techniques or…
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King of Kings

Randomized clinical trial There is no doubt that when doing a research in biomedicine we can choose from a large number of possible designs, all with their advantages and disadvantages. But in such a diverse and populous court, among jugglers,…
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From the hen to the egg

Case and control studies Surely someone overflowing genius has asked you on any occasion, with a smug look, what came first, the hen or the egg? Well, the next time you meet with someone like this, you can answer with…
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One about Romans

Cohort studies What a fellows, those Romans!. They came, they saw and they conquered. With those legions, each one with ten cohorts, each cohort with almost five hundred Romans with their skirts and strappy sandals. The cohorts were groups of…
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Which family you belong?

Classification of epidemiological studies As we already know from previous posts, the evidence-based medicine systematics begins with a knowledge gap that moves us to ask a structured clinical question. Once we have elaborated the question, we will use its components…
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Simplifying the impact

Other impact numbers In epidemiological studies it is common to find a set of measures of effect such as risks in exposed and non-exposed, relative risks and risk reductions. However, in order for the analysis of a study to be…
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The tribulations of an interval

NNT’s confidence interval The number needed to treat (NNT) is an impact measure that tells us in a simple way about the effectiveness of an intervention or its side effects. If the treatment tries to avoid unpleasant events, the NNT…
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Regular customers

Re-randomization in clinical trials We saw in a previous post that sample size is very important. The sample should be the right size, neither more nor less. If too large, we are wasting resources, something to keep in mind in…
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The fairground shotgun

Random and systematic error A few days ago I was with my cousin in our neighborhood parties and to entertain a while, we were firing a shot at one of the booths, to see if we could take the teddy…
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Together but not in each other’s pockets

Hybrid designs Observational studies are those in which, as its name suggests, the researcher merely observes what happens. Well, to observe and analyze, but has no active role on the exposure or intervention under study. Within these observational studies, we…
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