The underlying mathematical techniques behind the multivariate normal distribution are explained in principle and expanded in detail for up to three variables. The application of multivariate distributions to screening programs is described with particular reference to the calculation of risk ratios for the detection of Down's syndrome between 15 and 19 weeks of gestation.

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Neither a significant decrease in nocturnal urinary volumes nor an increase in urinary osmolality was achieved by doses of desmopressin > 20 micrograms. A dose of 60 g was associated with a decreased serum sodium level at the end of the 24-h period but there was no biochemical hyponatraemia. Because there were no benefits and a possibility of clinical hyponatraemia with higher doses, doses of > 20 micrograms desmopressin cannot be recommended.

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