  Young nearby moving groups are important and useful in many fields of
astronomy such as studying exoplanets, low-mass stars, and the stellar
evolution of the early planetary systems over tens of millions of years, which
has led to intensive searches for their members. Identification of members
depends on the used models sensitively, therefore, careful examination of the
models is required. In this study, we investigate the effects of the models
used in moving group membership calculations based on a Bayesian framework
(e.g., BANYAN II) focusing on the beta-Pictoris moving group (BPMG). Three
improvements for building models are suggested: (1) updating a list of accepted
members by re-assessing memberships in terms of position, motion, and age, (2)
investigating member distribution functions in $XYZ$, and (3) exploring field
star distribution functions in $XYZ$ and $UVW$. The effect of each change is
investigated, and we suggest using all of these improvements simultaneously in
future membership probability calculations. Using this improved MG membership
calculation and the careful examination of the age, 57 bona fide members of
BPMG are confirmed including 12 new members. We additionally suggest 17 highly
probable members.
