Marginal mean and 68% CL error bars on the parameters A_L (left) and N_eff (right) in ΛCDM extensions, estimated with different data choices for the Plik TT likelihood in comparison with results from alternate approaches or model, combined with a Gaussian prior on τ = 0.07 ± 0.02 (i.e., neither low-ℓ temperature nor polarization data). The “Plik TT+tauprior” case indicates the baseline (HM, ℓ_min = 30, ℓ_max = 2508), while the other cases are described in subsections of Sect. 4.1. The thin horizontal black line shows the baseline result and the thick dashed grey line displays the ΛCDM value (A_L = 1 and N_eff = 3.04). The grey bands show the standard deviation of the expected parameter shift, for those cases where the data used is a sub-sample of the baseline likelihood (see Eq. (53)).