condition mean min max ZT0-3 4.060595 1.481565 5.461365 ZT4-7 2.71801 2.71801 2.71801 ZT8-11 4.194695 4.194695 4.194695 ZT12-15 7.3239325 6.93077 7.7170950000000005 ZT16-19 9.262045 9.262045 9.262045 ZT20-23 9.16442 9.16442 9.16442