Table:
text: Wilkinson Microwave Anisotropy Probe
One-year data release
Best-fit cosmological parameters from WMAP one-year results
Parameter_ Symbol Best_fit_WMAP_only Best_fit_WMAP_extra_parameter Best_fit_all_data
Age of the universe ( Ga ) t_0 .4 ± .3 – .7 ± .2
Hubble`s constant ( km⁄ Mpc ·s ) H_0 ± ± + −
ic Baryon content Omega_b h^2 .024 ± .001 .023 ± .002 .0224 ± .0009
Matter content Omega_m h^2 .14 ± .02 .14 ± .02 .135 +.008 −.009
Optical depth to reionization tau .166 +.076 −.071 .20 ± .07 .17 ± .06
Amplitude A .9 ± .1 .92 ± .12 .83 +.09 −.08
Scalar spectral index n_s .99 ± .04 .93 +.07 −.07 .93 ± .03

text: Wilkinson Microwave Anisotropy Probe
One-year data release
Best-fit cosmological parameters from WMAP one-year results
Parameter_ Symbol Best_fit_WMAP_only Best_fit_WMAP_extra_parameter Best_fit_all_data
Running of spectral index dn_s / dk — −.047 ± .04 −.031 +.016 −.017
Fluctuation amplitude at 8h −1 Mpc sigma_8 .9 ± .1 — .84 ± .04
Total density of the universe Omega_{tot} – – .02 ± .02

Question: What is the parameter when the best fit (wmap only) is 0.9 ± 0.1, and the symbol is the cosmological best fit of the Wilkinson microwave anisotropy probe from the results of a year-long data release?