condition mean min max ZT0-3 8.387326 8.387326 8.387326 ZT4-7 8.5604805 8.5604805 8.5604805 ZT8-11 8.347315 8.347315 8.347315 ZT12-15 8.197016999999999 8.197016999999999 8.197016999999999 ZT16-19 7.872073 7.872073 7.872073 ZT20-23 8.856200000000001 8.856200000000001 8.856200000000001