PubMed1984
We chose, as typical values of serum cholesterol, the mean levels of the unimodal distribution of frequency with asymmetrical form, for different age groups, from some quarters of Palermo. We assumed as normal range estimate the interval between the 2.5 and 97.5 percentiles, with associated nonparametric 90% confidence intervals for normal limits for the true percentile. For this biometric analysis of ethnic physiology, we controlled the laboratory measurements in several inspection cycles. As the observed frequencies are not a real statistical sample, neither the 95% of the actual reference population: we smoothed the observed frequencies interpolating, with an algebraic polynomial, the mean empiric levels (and the chosen percentiles) of total serum cholesterol of the examined population - since the measurements taken on Mondays, the days after holidays, in January and April were chosen to see, experimentally, how the collected data depend on environmental alimentary factors; the degree of polynomial which gave the best approximation was chosen, on the grounds of the variance analysis; we tested the goodness of fit of the function to the referred frequencies. Moreover, the choice of the function was based on: a) the test of the hypothesis that the dependent variable reading the various specific ages, is normal, so we estimated the kurtosis and the asymmetry of the single frequency distributions; b) the simulation of the hypothesis that the measurements were made at random from gaussian distribution, so that the variances homogeneity of the examined character at various specific ages was examined by Bartlett's test. To identify the stages within which the cholesterolemic levels vary, due to growth and to the sexual maturation, we formed three age groups for males and four for females, whose delimitation is not arbitrary, since the best interpolation of the mean levels observed within such delimited age groups was again obtained by an algebraic polynomial of 2nd degree.