condition mean min max ZT0-3 8.427743628 7.377941362 9.477545894 ZT4-7 8.1717459355 7.490034873 8.853456998 ZT8-11 7.9922626075 6.847944109 9.136581106 ZT12-15 8.571845412333333 8.345414622 8.798276202666667 ZT16-19 9.1114233585 8.286642548 9.936204169 ZT20-23 9.453449867166666 9.376249934666667 9.530649799666666