Spot intensity time series data are accurately modeled by the logistic growth equation. Spot intensity data from a typical spot culture, on the edge of a cell array, were used to illustrate three different growth models. (a) Raw spot intensity is plotted versus time. Also plotted are the growth rate and specific growth rate, as calculated directly from the raw data. (b) A spline was used to fit the raw data from panel A. The raw data are plotted vs. time, along with the fitted growth curve, growth rate, and specific growth rate. (c) The logistic growth equation was used to fit the raw data and to calculate growth rate and specific growth rate. Refer to Tables 1 and 2 for comparison of cell proliferation phenotype values obtained by each model.