The linear range of the four cell enumeration assays using MDA-MB-231 cells. Four different cell enumeration assays were performed after 24 and 72 h incubation periods at six increasing starting cell densities. The solid line represents the linear least squares fit of the data. The dashed lines represent the 95% confidence bands. Graphs for 24 h incubation period depicts cell density up to 10 000 cells/well and 72 h incubation period depicts cell density up to 5 000 cells/well (n = 4).