condition mean min max ZT0-3 7.012794 7.012794 7.012794 ZT4-7 7.822086499999999 7.822086499999999 7.822086499999999 ZT8-11 7.6563935 7.6563935 7.6563935 ZT12-15 8.5214785 8.5214785 8.5214785 ZT16-19 7.3011669999999995 7.3011669999999995 7.3011669999999995 ZT20-23 7.8577555 7.8577555 7.8577555