highly significantp < 2.2 e - 16
The variance of differences for the genomic GC proportion in humans, mice, and fruit flies respectively is σ ^ n 2 = ( 0.000673 , 0.00055 , 0.00103 ) compared to σ ^ r 2 = ( 0.00469 , 0.00552 , 0.0021 ) for the permuted genome sequence, with the ratios being highly significant in all cases (F-test with p-value p < 2.2 e - 16 ).