condition mean min max ZT0-3 7.671887 7.671887 7.671887 ZT4-7 8.109920500000001 8.109920500000001 8.109920500000001 ZT8-11 8.0973005 8.0973005 8.0973005 ZT12-15 8.7381095 8.7381095 8.7381095 ZT16-19 8.0235085 8.0235085 8.0235085 ZT20-23 7.773521499999999 7.773521499999999 7.773521499999999