condition mean min max ZT0-3 6.735221666666667 5.79454 8.213735 ZT4-7 8.788465 8.788465 8.788465 ZT8-11 3.7443999999999997 3.7443999999999997 3.7443999999999997 ZT12-15 6.6560500000000005 6.563845000000001 6.748255 ZT16-19 4.399355 4.399355 4.399355 ZT20-23 6.00763 6.00763 6.00763