分析答题响应时间与记忆强度关系

solve()

Response time vs quality:
  instant(<2s): count=397 again_rate=5.8% {'Again': np.int64(23), 'Easy': np.int64(76), 'Good': np.int64(230), 'Hard': np.int64(68)}
  normal(5-10s): count=1313 again_rate=4.5% {'Again': np.int64(59), 'Easy': np.int64(324), 'Good': np.int64(746), 'Hard': np.int64(184)}
  quick(2-5s): count=831 again_rate=5.4% {'Again': np.int64(45), 'Easy': np.int64(219), 'Good': np.int64(427), 'Hard': np.int64(140)}
  slow(>10s): count=1368 again_rate=4.7% {'Again': np.int64(64), 'Easy': np.int64(333), 'Good': np.int64(775), 'Hard': np.int64(196)}