Resumen

HERNANDEZ BLANCO, Javier. Sample size for a clinic trial. Rev Col Gastroenterol [online]. 2006, vol.21, n.2, pp.118-121. ISSN 0120-9957.

In the design of an investigation we possess several tools like computer programs, statistical ecuations and simple mathematical formulae to be able to determine the adecuate sample size, which in turn will allow us to infer the value of a parameter in the population. Ideally, we should evaluate the whole eligible population but for reasons of cost and time the studies must be done from a sample of this population. The selection of the sample has ethical implications and influences the power of the study to detect differences when they exist. With some practice, it is possible to come to calculate in an adecuate way the necessary sample size. This review will contribute useful information to bear in mind when calculating the sample size.

Palabras clave : Sample size; alpha error; power of the study.

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