condition mean min max ZT0-3 31.327989 31.327989 31.327989 ZT4-7 29.129159 29.129159 29.129159 ZT8-11 31.877347999999998 31.877347999999998 31.877347999999998 ZT12-15 23.533644000000002 23.533644000000002 23.533644000000002 ZT16-19 20.381584 20.381584 20.381584 ZT20-23 24.432881000000002 24.432881000000002 24.432881000000002