condition mean min max ZT0-3 2.972265 2.972265 2.972265 ZT4-7 2.264965 2.264965 2.264965 ZT8-11 3.75715 3.75715 3.75715 ZT12-15 3.64418 3.64418 3.64418 ZT16-19 4.83087 4.83087 4.83087 ZT20-23 3.96494 3.96494 3.96494