i performed codon based z-test for two genes to compare selective constraints between species groups ( purifying selection (dN < dS) as alternative hypotheses to the null hypotheses of strict neutrality (dN = dS)). Now i have Z statistic values which are slightly different between the groups. See example
Z statistic p value gene A group 1 3.262 0.001 group 2 2.964 0.002 gene B group 1 3.062 0.005 group 2 4.964 0.001
My question regards the strength of selection constraints acting on the different groups. Is it that in group 1 for gene A selection acts stronger? When we compare ka/ks ratios, i know that lower values would indicate stronger selection, like in this example for Group 2:
Gene A ka/ks p value Group1 0.033 <0.001 Group2 0.027 <0.001
I am happy about any help!