Table 3.

Comparison of cross-validation results for predicting promoters and enhancers.

Combination	Promoter PPVa (standard deviation)	Enhancer PPV (standard deviation)
HMM method using 6 histone signaturesb	97.87% (1.06)	93.52%(1.83)
HMM method using 2 histone signaturesc	95.46% (2.82)	94.06% (0.89)
Heintzman et al. using 6 histone signatures	96%	78%
Heintzman et al. using 2 histone signatures	95%	85%

^aPositive predictive value (PPV) = true prediction/(true prediction + wrong prediction) and standard deviation are calculated.

^b6 histone signatures: H4ac, H3ac, H3Kme1, H3K4me2, H3K4me3, H3

^c2 histone signatures: H3Kme1, H3K4me3