“…In principle, the use of the normalized power prior does not necessarily assume a proper initial prior on
, whereas an improper initial prior often results in a similar normalized power prior after incorporating information from D 0 . Moreover, if
is improper, the power prior may not be proper for all
, even for the commonly used reference priors (Han et al.,
2022). As a result, the starting point δ 1 may not be close to 0 and can vary case by case.…”