Threshold Correlation Coefficient and Sensitivity vs. Number of Microarrays Labeled data points represent selected subsets as follows: A – starvation, B – cell cycle, C – stress response, D – all data. All other data points, marked by blue ●, indicate the mean value for 10 randomly selected data sets of the given size. The bars show one standard deviation. The curves shown are fit using only the randomly chosen subsets. A) The threshold correlation coefficient r, chosen such that 75% of all gene pairs with correlation greater than r share a common transcription factor, decreases as the number of microarrays increases. B) Sensitivity (the ratio of the number of gene pairs which both share a common transcription factor and have an expression correlation greater than r to the total number of gene pairs which share a common transcription factor) when threshold correlation is chosen such that positive predictive value is 75%, increases with the number of microarrays used up to a limit of 2.8%. Random sets of microarrays showed greater sensitivity for finding gene pairs bound by a common transcription factor than predetermined sets of microarrays.