  We review the constraints given by the linear matter power spectra data on
cosmological and bias parameters, comparing the data from the PSCz survey
(Hamilton et al., 2000) and from the matter power spectrum infered by the study
of Lyman alpha spectra at z=2.72 (Croft et al., 2000). We consider
flat--$\Lambda$ cosmologies, allowing $\Lambda$, $H_0$ and $n$ to vary, and we
also let the two ratio factors $r_{pscz}$ and $r_{lyman}$ ($r^2_i =
\frac{P_{i}(k)}{P_{CMB}(k)}$) vary independently. Using a simple $\chi^2$
minimisation technique, we find confidence intervals on our parameters for each
dataset and for a combined analysis. Letting the 5 parameters vary freely gives
almost no constraints on cosmology, but requirement of a universal ratio for
both datasets implies unacceptably low values of $H_0$ and $\Lambda$. Adding
some reasonable priors on the cosmological parameters demonstrates that the
power derived by the PSCz survey is higher by a factor $\sim 1.75$ compared to
the power from the Lyman $\alpha$ forest survey.
