condition mean min max ZT0-3 7.978306 7.978306 7.978306 ZT4-7 7.673695 7.673695 7.673695 ZT8-11 8.047508 8.047508 8.047508 ZT12-15 8.428923000000001 8.428923000000001 8.428923000000001 ZT16-19 7.87747 7.87747 7.87747 ZT20-23 7.954122 7.954122 7.954122