condition mean min max ZT0-3 8.684387 8.684387 8.684387 ZT4-7 8.1847965 8.1847965 8.1847965 ZT8-11 8.4767865 8.4767865 8.4767865 ZT12-15 8.7967735 8.7967735 8.7967735 ZT16-19 8.796426499999999 8.796426499999999 8.796426499999999 ZT20-23 8.5427045 8.5427045 8.5427045