condition mean min max ZT0-3 7.053095 7.053095 7.053095 ZT4-7 8.435199 8.435199 8.435199 ZT8-11 7.165578 7.165578 7.165578 ZT12-15 8.621319499999998 8.621319499999998 8.621319499999998 ZT16-19 7.515369 7.515369 7.515369 ZT20-23 7.488506 7.488506 7.488506