condition mean min max ZT0-3 8.446746 8.446746 8.446746 ZT4-7 9.8084305 9.8084305 9.8084305 ZT8-11 9.359206499999999 9.359206499999999 9.359206499999999 ZT12-15 9.306292 9.306292 9.306292 ZT16-19 9.166155499999999 9.166155499999999 9.166155499999999 ZT20-23 9.0763505 9.0763505 9.0763505