condition mean min max ZT0-3 15.202475 15.202475 15.202475 ZT4-7 15.522461 15.522461 15.522461 ZT8-11 17.2154285 17.2154285 17.2154285 ZT12-15 15.964703499999999 15.964703499999999 15.964703499999999 ZT16-19 24.130434 24.130434 24.130434 ZT20-23 19.810163 19.810163 19.810163