condition mean min max ZT0-3 7.961489 7.961489 7.961489 ZT4-7 8.3673215 8.3673215 8.3673215 ZT8-11 7.714949 7.714949 7.714949 ZT12-15 8.8360885 8.8360885 8.8360885 ZT16-19 7.195285999999999 7.195285999999999 7.195285999999999 ZT20-23 7.987773499999999 7.987773499999999 7.987773499999999