condition mean min max ZT0-3 2.168264 2.168264 2.168264 ZT4-7 5.344741 5.344741 5.344741 ZT8-11 2.267366 2.267366 2.267366 ZT12-15 1.5112393333333334 1.5112393333333334 1.5112393333333334 ZT16-19 6.889998 6.889998 6.889998 ZT20-23 2.6860459999999997 2.6860459999999997 2.6860459999999997