condition mean min max ZT0-3 2.103135 2.103135 2.103135 ZT4-7 1.707535 1.707535 1.707535 ZT8-11 2.410275 2.410275 2.410275 ZT12-15 1.6354090000000001 1.6354090000000001 1.6354090000000001 ZT16-19 4.23534 4.23534 4.23534 ZT20-23 2.438415 2.438415 2.438415