condition mean min max ZT0-3 8.859805 8.859805 8.859805 ZT4-7 7.0938099999999995 7.0938099999999995 7.0938099999999995 ZT8-11 6.68054 6.68054 6.68054 ZT12-15 8.420465 8.420465 8.420465 ZT16-19 11.51825 11.51825 11.51825 ZT20-23 9.610175 9.610175 9.610175