  We perform a Markov Chain Monte Carlo (MCMC) statistical analysis of a number
of measured ground-state-to-ground-state single $\beta^+$/electron-capture and
$\beta^-$ decays in the nuclear mass range A = 62 - 142. The corresponding
experimental comparative half-lives (log ft values) are compared with the
theoretical ones obtained by the use of the proton-neutron quasiparticle
random-phase approximation (pnQRPA) with G-matrix based effective interactions.
The MCMC analysis is performed separately for 47 isobaric triplets and 28 more
extended isobaric chains of nuclei to extract values and uncertainties for the
effective axial-vector coupling constant g_A in nuclear-structure calculations
performed in the pnQRPA framework. As far as available, measured half-lives for
two-neutrino double beta-minus decays occurring in the studied isobaric chains
are analyzed as well.
