condition mean min max ZT0-3 6.775385 6.775385 6.775385 ZT4-7 4.073165 4.073165 4.073165 ZT8-11 5.72123 5.72123 5.72123 ZT12-15 7.4708000000000006 7.4708000000000006 7.4708000000000006 ZT16-19 12.02885 12.02885 12.02885 ZT20-23 8.604735 8.604735 8.604735