The current accelerated expansion of the Universe can be explained either by dark energy or by modified gravity theories. Both of them explain the exact same back ground evolution of the Universe. This degeneracy can be broken when the observation of large scale structure formation is taken into account. Two observables are parameterized by the so-called dark energy equation of state, ω and the growth index parameter, γ. From these observed parameters, one can reconstruct the model parameters of one of the modified gravity theoreis, so-called the scalar-tensor gravity theories. Especially, the scalar tensor gravity theories can be described both in Jordan frame and in Einstein frame. We show that if cosmological observations are interpreted in one frame, then all of observables should be interpreted in that frame. This explicitly shows that conformal inequality of cosmological observables.