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 |