condition mean min max ZT0-3 7.867544 7.867544 7.867544 ZT4-7 8.6342865 8.6342865 8.6342865 ZT8-11 7.719213 7.719213 7.719213 ZT12-15 8.216524 8.216524 8.216524 ZT16-19 8.259788499999999 8.259788499999999 8.259788499999999 ZT20-23 8.581443499999999 8.581443499999999 8.581443499999999