condition mean min max ZT0-3 8.716958 8.716958 8.716958 ZT4-7 8.774441 8.774441 8.774441 ZT8-11 8.175347 8.175347 8.175347 ZT12-15 7.871413 7.871413 7.871413 ZT16-19 8.67935 8.67935 8.67935 ZT20-23 7.9779634999999995 7.9779634999999995 7.9779634999999995