condition mean min max ZT0-3 2.7477275 2.4288 3.066655 ZT4-7 2.27344 2.27344 2.27344 ZT8-11 3.5912249999999997 3.5912249999999997 3.5912249999999997 ZT12-15 0 0 0 ZT16-19 4.410679999999999 4.410679999999999 4.410679999999999 ZT20-23 6.276845 6.276845 6.276845