condition mean min max ZT0-3 2.238835 2.238835 2.238835 ZT4-7 2.21279 2.21279 2.21279 ZT8-11 2.330705 2.330705 2.330705 ZT12-15 1.8103150000000001 1.8103150000000001 1.8103150000000001 ZT16-19 2.224815 2.224815 2.224815 ZT20-23 1.6641949999999999 1.6641949999999999 1.6641949999999999