condition mean min max ZT0-3 8.361231 8.361231 8.361231 ZT4-7 10.80442 10.80442 10.80442 ZT8-11 7.7566605 7.7566605 7.7566605 ZT12-15 7.7418445 7.7418445 7.7418445 ZT16-19 8.042100999999999 8.042100999999999 8.042100999999999 ZT20-23 8.2094695 8.2094695 8.2094695