condition mean min max ZT0-3 7.592228 7.592228 7.592228 ZT4-7 8.249122 8.249122 8.249122 ZT8-11 8.452424 8.452424 8.452424 ZT12-15 8.2905505 8.2905505 8.2905505 ZT16-19 7.7856245 7.7856245 7.7856245 ZT20-23 8.581436 8.581436 8.581436