condition mean min max ZT0-3 7.820455 7.820455 7.820455 ZT4-7 7.5599875 7.5599875 7.5599875 ZT8-11 7.597943 7.597943 7.597943 ZT12-15 7.7083569999999995 7.7083569999999995 7.7083569999999995 ZT16-19 7.7726015 7.7726015 7.7726015 ZT20-23 7.746171 7.746171 7.746171