Table 1.

Compression in microarray measurements. The compression depends on the fold-of-change, and exhibits complex characteristics when the spot TD intensity falls below 5,000 RFU/pixel. Data presented are from the spiked-in Arabidopsis in vitro transcripts in experiment1. At each input ratio, the mean compression factor (ratio between the measured and input ratio) is determined for all spots with TD intensity above 5,000 RFU/pixel, and a linear regression is performed between the compression and the spot TD intensity for all spots below 5,000 RFU/pixel, in the same fashion as described in figure 1

Input ratio (Cy5:Cy3)	Compression factor for spots > 5,000 RFU/pixel	Slope of linear regression (< 5,000 RFU/pixel)
30:1	0.18	0.78 (R2~0.82, p < 0.0001)
10:1	0.77	0.42 (R2~0.62, p < 0.0001)
5:1	0.87	0.27 (R2~0.46, p < 0.0001)
1:1	1.05	0.10 (R2~0.30, p < 0.03)
1:5	0.86	0.05 (R2~0.04, p < 0.06)
1:10	0.84	0.14 (R2~0.18, p < 0.0001)
1:30	0.55	0.27 (R2~0.77, p < 0.0001)