condition mean min max ZT0-3 7.924803 7.924803 7.924803 ZT4-7 7.8681705 7.8681705 7.8681705 ZT8-11 8.1363995 8.1363995 8.1363995 ZT12-15 9.1696345 9.1696345 9.1696345 ZT16-19 7.6642185000000005 7.6642185000000005 7.6642185000000005 ZT20-23 9.2182075 9.2182075 9.2182075