condition mean min max ZT0-3 7.196092 7.196092 7.196092 ZT4-7 7.4909615 7.4909615 7.4909615 ZT8-11 8.597916000000001 8.597916000000001 8.597916000000001 ZT12-15 8.4255405 8.4255405 8.4255405 ZT16-19 8.0974055 8.0974055 8.0974055 ZT20-23 8.107046 8.107046 8.107046