condition mean min max ZT0-3 7.25 7.25 7.25 ZT4-7 1.7 1.7 1.7 ZT8-11 4.4 4.4 4.4 ZT12-15 8.9 8.9 8.9 ZT16-19 8.399999999999999 8.399999999999999 8.399999999999999 ZT20-23 5.75 5.75 5.75