condition mean min max ZT0-3 7.8 7.8 7.8 ZT4-7 8.1 8.1 8.1 ZT8-11 9.45 9.45 9.45 ZT12-15 11.85 11.85 11.85 ZT16-19 14.149999999999999 14.149999999999999 14.149999999999999 ZT20-23 19.3 19.3 19.3