Detectability of the solar cycle in individual skip travel times. (A) Amplitudes of travel-time variations due to the solar cycle, A_s, versus skip number s (see Eq. (18)), with error bars of (see Eq. (19)). (B) Signal-to-noise ratios . (C) Variance of travel-time noise . (D) Plot of Λ_{s, s′ = 19} and (E) plot of R_{s, s′ = 19}. In all panels, the blue and red points show the even and odd values of s.