condition mean min max ZT0-3 6.663995 6.431345 6.8966449999999995 ZT4-7 7.0801300000000005 7.0801300000000005 7.0801300000000005 ZT8-11 6.60783 6.60783 6.60783 ZT12-15 0 0 0 ZT16-19 7.8188949999999995 7.8188949999999995 7.8188949999999995 ZT20-23 7.874395 7.874395 7.874395