Table 4.

Affymetrix spike experiment

Transcript	Experiments
	M, N, O, P	Q, R, S, T
1	512	1,024
2	1,024	0
3	0	0.25
4	0.25	0.5
5	0.5	1
6	1	2
7	2	4
8	4	8
9	8	16
10	16	32
11	32	64
12	512	1024
13	128	256
14	256	512

The table shows the part of the design of the Affymetrix spike experiment used as a testing ground for methods of ranking genes with respect to differential expression. Out of the 12,626 probe sets on the U95A array 14 transcripts have been spiked at known quantities in picomols selected according to a Latin square design. Here 'experiment' (M, N, O..., T) refers to a set of three arrays with the same spiking. The numbers indicate the amount of spike transcript in pM.