condition mean min max ZT0-3 9.233933 9.233933 9.233933 ZT4-7 8.0822665 8.0822665 8.0822665 ZT8-11 9.092838 9.092838 9.092838 ZT12-15 8.5143115 8.5143115 8.5143115 ZT16-19 8.913887500000001 8.913887500000001 8.913887500000001 ZT20-23 8.271998 8.271998 8.271998