condition mean min max ZT0-3 8.323995 8.323995 8.323995 ZT4-7 3.687675 3.687675 3.687675 ZT8-11 2.8667499999999997 2.8667499999999997 2.8667499999999997 ZT12-15 3.6591949999999995 3.6591949999999995 3.6591949999999995 ZT16-19 5.6144099999999995 5.6144099999999995 5.6144099999999995 ZT20-23 9.731925 9.731925 9.731925