condition mean min max ZT0-3 18.112676 18.112676 18.112676 ZT4-7 20.524983 20.524983 20.524983 ZT8-11 17.076428999999997 17.076428999999997 17.076428999999997 ZT12-15 16.400123 16.400123 16.400123 ZT16-19 15.563531000000001 15.563531000000001 15.563531000000001 ZT20-23 16.959676 16.959676 16.959676