Prior and SELFI posteriors for the initial matter power spectrum θ given the observations Φ_O. The ground truth θ_gt is indicated by the dashed blue line. The prior and posterior means, θ₀, γ_A and γ_B, are represented respectively by the yellow, green and red lines, along with their 2σ credible regions (shaded yellow, green, and red areas). The vertical dashed lines indicate the support wave numbers for the initial matter power spectrum representation. The posterior obtained with the well-specified Model A is unbiased over all scales, whilst the posterior obtained with the misspecified Model B exhibits an excess and a lack of power at the largest and smallest scales, respectively.