This data analysis tool calculates concentrations using a Four Parameter Logistic (4PL) curve fit in accordance with DIAsource's 25OH Vitamin D Total ELISA kit. The standard data points are plotted (concentration vs. OD) on semi-log axes and a 4PL curve is fitted through these points. The concentrations of the unknown samples are determined from the fit and any specified dilution factors are applied. The %CV, Standard Deviation and Standard Error are calculated for each replicated sample. Samples outside the range of the standards or the fit (greater than the upper asymptote or below the lower asymptote) are highlighted in yellow.