condition mean min max ZT0-3 6.3943821849999996 6.181348666 6.607415703999999 ZT4-7 7.151184544 7.097305063333334 7.205064024666667 ZT8-11 8.5999635055 8.226019054333333 8.973907956666666 ZT12-15 9.127512841000001 8.936061129 9.318964553 ZT16-19 8.938675191166666 8.450854964333333 9.426495418 ZT20-23 7.030714512166666 6.335739399333333 7.725689625