condition mean min max ZT0-3 7.756590000000001 6.541495 8.971685 ZT4-7 6.719695 6.719695 6.719695 ZT8-11 16.975949999999997 16.975949999999997 16.975949999999997 ZT12-15 0 0 0 ZT16-19 17.401400000000002 17.401400000000002 17.401400000000002 ZT20-23 11.9149 11.9149 11.9149