condition mean min max ZT0-3 15.374591 15.374591 15.374591 ZT4-7 15.5672155 15.5672155 15.5672155 ZT8-11 14.8695655 14.8695655 14.8695655 ZT12-15 15.8870105 15.8870105 15.8870105 ZT16-19 15.311857499999999 15.311857499999999 15.311857499999999 ZT20-23 15.336281 15.336281 15.336281