condition mean min max ZT0-3 18.897961 18.897961 18.897961 ZT4-7 15.358531 15.358531 15.358531 ZT8-11 17.955141 17.955141 17.955141 ZT12-15 16.018991 16.018991 16.018991 ZT16-19 17.8582975 17.8582975 17.8582975 ZT20-23 17.779947999999997 17.779947999999997 17.779947999999997