condition mean min max ZT0-3 8.775441 8.775441 8.775441 ZT4-7 8.2975805 8.2975805 8.2975805 ZT8-11 8.866021 8.866021 8.866021 ZT12-15 8.280409500000001 8.280409500000001 8.280409500000001 ZT16-19 8.544881499999999 8.544881499999999 8.544881499999999 ZT20-23 9.086618 9.086618 9.086618