condition mean min max ZT0-3 8.527508 8.527508 8.527508 ZT4-7 8.4070405 8.4070405 8.4070405 ZT8-11 8.749409499999999 8.749409499999999 8.749409499999999 ZT12-15 8.709011 8.709011 8.709011 ZT16-19 9.274514 9.274514 9.274514 ZT20-23 7.7226425 7.7226425 7.7226425