For decades , H _ { 0 } and q _ { 0 } were the quest of cosmology , as they promised to characterize our “ world model ” without reference to a specific cosmological framework .
Using Monte Carlo simulations , we show that q _ { 0 } can not be directly measured using distance indicators with both accuracy ( without offset away from its true value ) and precision ( small error bar ) .
While H _ { 0 } can be measured with accuracy and precision , to avoid a small bias in its direct measurement ( of order 5 % ) we demonstrate that the pair H _ { 0 } and \Omega _ { M } ( assuming flatness and w = -1 ) is a better choice of two parameters , even if our world model is not precisely \Lambda CDM .
We illustrate with analysis of the Constitution set of supernovae and indirectly infer q _ { 0 } = -0.57 \pm - 0.04 .
Finally , we show that it may be possible to directly determine q _ { 0 } with both accuracy and precision using the time dependence of redshifts ( “ redshift drift ” ) .