condition mean min max ZT0-3 6.68058 6.68058 6.68058 ZT4-7 8.21364 8.21364 8.21364 ZT8-11 7.926245 7.926245 7.926245 ZT12-15 7.3364650000000005 7.3364650000000005 7.3364650000000005 ZT16-19 7.63138 7.63138 7.63138 ZT20-23 8.21255 8.21255 8.21255