condition mean min max ZT0-3 7.901987 7.901987 7.901987 ZT4-7 8.709047 8.709047 8.709047 ZT8-11 8.6223365 8.6223365 8.6223365 ZT12-15 8.4801185 8.4801185 8.4801185 ZT16-19 6.733670500000001 6.733670500000001 6.733670500000001 ZT20-23 7.4396895 7.4396895 7.4396895