Table II. Distribution of marker proteins or ceramide during neuroprogenitor formation (NP2 stage).

Marker		Counts	Percentage of total counts (n = 200)	Percent expected if independently distributed
A	B		A + B	f(A + B) = f(A) × f(B)
PAR-4 + Nestin			12 ± 4	6%	25%
PAR-4 + Ceramide			62 ± 7	31%	24%
PAR-4 + Nestin			50 ± 7	25%	30%

Differentiating ES cells were grown on coverslips and treated as described in the legend for Table I. Table II shows double-staining experiments for two markers as indicated (A + B represents cells that are double-stained for A and B). The percentage of cells in the last column has been calculated from the frequency of each marker (A or B) in the total population of cells as described in the “Statistical Analysis” section of Materials and methods. Standard means and variation for five areas with 200 cells from three independent experiments is shown.