condition mean min max ZT0-3 19.467075 18.58445 20.3497 ZT4-7 17.1278 17.1278 17.1278 ZT8-11 15.6711 15.6711 15.6711 ZT12-15 0 0 0 ZT16-19 19.4333 19.4333 19.4333 ZT20-23 20.15985 20.15985 20.15985