condition mean min max ZT0-3 6.620969 6.620969 6.620969 ZT4-7 6.6257 6.6257 6.6257 ZT8-11 7.716573 7.716573 7.716573 ZT12-15 8.9285 8.9285 8.9285 ZT16-19 7.529313999999999 7.529313999999999 7.529313999999999 ZT20-23 8.45594 8.45594 8.45594