condition mean min max ZT0-3 7.919485 7.28643 8.55254 ZT4-7 6.26745 6.26745 6.26745 ZT8-11 4.58544 4.58544 4.58544 ZT12-15 0 0 0 ZT16-19 7.972535000000001 7.972535000000001 7.972535000000001 ZT20-23 8.707635 8.707635 8.707635