Comparison of the fitting formula to the numerical results of CMB fast (Seljak & Zaldarriaga 1996). Results at (a) ﹩z=0﹩, (b) ﹩z=9﹩. Upper panels: Transfer functions divided by a fiducial pure CDM transfer function, formed by using eq. (18) with ﹩\alpha _{\nu }=\beta _{c}=1﹩ and ﹩q_{\mathrm{eff}\,}=q﹩. Density‐weighted CDM + baryon (short‐dashed line) and CDM + baryon + neutrino (long‐dashed line) transfer functions are shown. Lower panels: Fractional residuals. The cosmology is ﹩\Omega _{0}=1﹩, ﹩\Omega _{\nu }=0.2﹩, ﹩\Omega _{b}=0.05﹩, and ﹩h=0.5﹩.