  Bar fractions depend on the properties of the host galaxies, which are
closely related to the formation and evolution of bars. However, observational
studies do not provide consistent results. We investigate the bar fraction and
its dependence on the properties of the host galaxies by using three bar
classification methods: visual inspection, ellipse fitting method, and Fourier
analysis. Our volume-limited sample consists of 1,698 spiral galaxies brighter
than $M_{\rm r}=-15.2$ with $z < 0.01$ from SDSS/DR7 visually classified by Ann
et al. (2015). We first compare the consistency of classification among the
three methods. Automatic classifications detect visually determined strongly
barred galaxies with the concordance of $74\% \sim 85\%$. However, they have
some difficulty in identifying bars, in particular, in bulge-dominated
galaxies, which affects the distribution of bar fraction as a function of the
Hubble type. We obtain, for the same sample, different bar fractions of 63%,
48%, and 36% by visual inspection, ellipse fitting, and Fourier analysis,
respectively. The difference is mainly due to how many weak bars are included.
Moreover, we find the different dependence of bar fraction on the Hubble type
for strong versus weak bars: SBs are preponderant in early-type spirals whereas
SABs in late-type spirals. This causes a contradictory dependence on host
galaxy properties when different classification methods are used. We propose
that strong bars and weak bars experience different processes for their
formation, growth, and dissipation by interacting with different inner galactic
structures of early-type and late-type spirals.
