condition mean min max ZT0-3 7.203708 7.203708 7.203708 ZT4-7 6.960575 6.960575 6.960575 ZT8-11 7.117037 7.117037 7.117037 ZT12-15 7.9440475 7.9440475 7.9440475 ZT16-19 7.380359 7.380359 7.380359 ZT20-23 7.404292 7.404292 7.404292