condition mean min max ZT0-3 12.863983333333334 7.82785 16.09925 ZT4-7 6.892465 6.892465 6.892465 ZT8-11 6.2483450000000005 6.2483450000000005 6.2483450000000005 ZT12-15 14.37675 13.051649999999999 15.70185 ZT16-19 16.1345 16.1345 16.1345 ZT20-23 20.84865 20.84865 20.84865