condition mean min max ZT0-3 18.250975 17.7011 18.80085 ZT4-7 20.14255 20.14255 20.14255 ZT8-11 15.876999999999999 15.876999999999999 15.876999999999999 ZT12-15 0 0 0 ZT16-19 18.6814 18.6814 18.6814 ZT20-23 17.7603 17.7603 17.7603