condition mean min max ZT0-3 8.223484 8.223484 8.223484 ZT4-7 8.808072 8.808072 8.808072 ZT8-11 8.3802095 8.3802095 8.3802095 ZT12-15 8.093322 8.093322 8.093322 ZT16-19 8.342499 8.342499 8.342499 ZT20-23 9.085265 9.085265 9.085265