Transformation in the PC-aided biochemical data analysis

Data transformations enable expression of original data in a new scale, mor e suitable for data analysis. in computer-aided interactive analysis of bio chemical and clinical data an exploratory data analysis often finds that th e sample distribution is systematically skewed or does not accept a sample homogeneity. Under such circumstances the original data should be transform ed. The power transformation and the Box-Cox transformation improve sample symmetry and also stabilize variance. Both the Hines-Hines selection graph and the plot of logarithm of a maximum likelihood function allow selection of an optimum transformation parameter. The proposed procedure of data tran sformation in univariate data analysis is illustrated on a determination of 17-hydroxypregnenolone in umbilical blood of a population of newborns. Low er levels of free 5-ene steroids in umbilical blood and elevated levels of 5-ene steroid sulfates indicate a congenital sex-specific placental sulfata se insufficiency. After examination of statistical assumptions by diagnosti c plots of an exploratory data analysis the best estimate of a mean value o f 17-hydroxypregnenolone is derived.