Besides the literature on the subject matter and other sources may give us an idea about the expected value of the proportion (one that probably will), or in the worst case scenario you can choose the most unfavorable situation for the calculation of sample size (the value of the possible values near to 50% or 50% when the prevalence is unknown).Īlso you should keep in mind the size of the population, because with small populations (less than 1000 individuals), it is possible to obtain a larger sample size than the size of the population, and for this reason then you must make a adjust. It should be taking into account that the error usually accepted and the confidence level are set arbitrarily by the researcher. In these cases the sample size depends on the acceptable error, the desired confidence level or probability of getting a correct answer, and the expected prevalence. Si presionas 'generar muestras', aproximadamente el.
90, y si o no contiene la media poblacional. Presiona 'generar muestras' para abrir una ventana que da el número indicado de muestras de tamaño. EJEMPLO 1 Estimacin de la media poblacional en una subpoblacin. Not all the studies are focused in determining the presence of disease in a population, moreover there are studies interested in establishing a ratio (for example, knowing how many diseased individuals are, i.e., prevalence). Ejemplo 2 Ilustración de intervalos de confianza. fumadores en una poblacin, y tambin estimar dicho porcentaje para HOMBRES y para. Sample size: Estimate proportion (random sampling & perfect diagnostic)Īvailable variables In order to determine minimum sample size needed to estimate a proportion depending on expected value and accepted error (desired precision), you must indicate which are the variables that have information: Maximum possible prevalence (all negative samples) Para determinar el intervalo de confianza utilizaremos la siguiente formula: Lo cual significa que la media poblacional, con un nivel de confianza de 95 se encontrara en el intervalo dado por: Por tanto, con 95 de confianza, la media poblacional se encontrara en el intervalo: 18.6084 µ 21.3916 7.
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