From: A comparison of Affymetrix gene expression arrays
U133
HuEx
HuGene
Average Number of Probes per Gene
16.1
44.8
26.8
Average Number of Probes per Exon
-
5.8
3.7
Median Probe-Level Variance
0.139
0.306
0.308
Median Exon-Level Variance
0.086
0.119
Median Gene-Level Variance
0.015
0.035
0.020