condition mean min max ZT0-3 6.886775 6.886775 6.886775 ZT4-7 4.75232 4.75232 4.75232 ZT8-11 4.966565 4.966565 4.966565 ZT12-15 7.988415 7.988415 7.988415 ZT16-19 8.932485 8.932485 8.932485 ZT20-23 8.23954 8.23954 8.23954