Change in θ with SNR (in bins of 20) for the repeat observations within TGMA (black symbols) compared with the σ(θ)_int values (Sect. 5) for TGMA (grey points). a) The ΔT_eff that 70% of the repeat sample were less than or equal to at each SNR (black squares). The trend with SNR is shown by the black lines. b) As for a) but for variations in log g (black stars). c) As for a) but for variations in [M/H] (black circles). d) As for a) but for variations in [α/Fe] (black diamonds).