condition mean min max ZT0-3 8.873985 8.873985 8.873985 ZT4-7 9.5168775 9.5168775 9.5168775 ZT8-11 8.5430055 8.5430055 8.5430055 ZT12-15 9.000467 9.000467 9.000467 ZT16-19 8.7733355 8.7733355 8.7733355 ZT20-23 8.6189535 8.6189535 8.6189535