condition mean min max ZT0-3 4.253138333333333 1.965455 5.684395 ZT4-7 1.38807 1.38807 1.38807 ZT8-11 2.49517 2.49517 2.49517 ZT12-15 3.4089825 2.640385 4.17758 ZT16-19 4.1077650000000006 4.1077650000000006 4.1077650000000006 ZT20-23 6.280905 6.280905 6.280905