  Statistical dependencies among features of coronal mass ejections (CMEs),
solar flares, and sigmoidal structures in soft-X-ray images were investigated.
We applied analysis methods to all the features in the same way in order to
investigate the reproducibility of the correlations among them, which may be
found from the combination of previous statistical studies. The samples of 211
M-class and X-class flares, which were observed between 2006 and 2015 by
Hinode/X-ray telescope, Solar and Heliospheric Observatory/Large Angle and
Spectrometric Coronagraph, and GOES, were examined statistically. Five kinds of
analysis were performed: Occurrence rate analysis, linear-correlation analysis,
association analysis, the Kolmogorov--Smirnov test, and Anderson-Darling test.
The analyses show three main results. First, the sigmoidal structure and long
duration events (LDEs) has stronger dependency on the CME occurrence than large
X-ray class events in on-disk events. Second, for the limb events, the
significant dependency exists between LDEs and CME occurrence, and between
X-ray class and CME occurrence. Third, there existed 32.4% of on-disk flare
events, which had sigmoidal structure and were not accompanied by CMEs.
However, the occurrence probability of CMEs without sigmoidal structures is
very small, 8.8 %, in on-disk events. While the first and second results are
consistent with previous studies, we newly provided the difference between the
on-disk events and limb events. The third result that non-sigmoidal regions
produce less eruptive events is also different from previous results. We
suggest that sigmoidal structures in soft X-ray images will be a helpful
feature for CME prediction regarding on-disk flare events.
