Using the relation between distance modulus (m−M) and redshift z, deduced from Friedman- Robertson-Walker (FRW) metric and assuming different values of deceleration parameter q0. We constrained the Hubble parameter h. The estimates of the Hubble parameters we obtained using the median values of the data obtained from NASA Extragalactic Database (NED), are: h=0.7±0.3, for q0=0, h=0.6±0.3, for q0=1 and h=0.8±0.3 , for q0=−1. The corresponding age τ and size R of the observable universe were also estimated as: τ=15±1 Gyr, R=(5±2)×103 Mpc, τ=18±1 Gyr, R=(6±2)×103 Mpc and τ=13±1 Gyr, R=(4±2)×103 Mpc for q0=0, q0=1 and q0=−1 respectively
