condition mean min max ZT0-3 1.999415 1.869195 2.129635 ZT4-7 2.3438 2.3438 2.3438 ZT8-11 2.8286249999999997 2.8286249999999997 2.8286249999999997 ZT12-15 0 0 0 ZT16-19 3.75413 3.75413 3.75413 ZT20-23 3.246 3.246 3.246