condition mean min max ZT0-3 9.273785 9.273785 9.273785 ZT4-7 8.687199 8.687199 8.687199 ZT8-11 9.187430500000001 9.187430500000001 9.187430500000001 ZT12-15 8.427844499999999 8.427844499999999 8.427844499999999 ZT16-19 8.6256545 8.6256545 8.6256545 ZT20-23 8.8495245 8.8495245 8.8495245