condition mean min max ZT0-3 7.423385 7.423385 7.423385 ZT4-7 6.783495 6.783495 6.783495 ZT8-11 4.5847999999999995 4.5847999999999995 4.5847999999999995 ZT12-15 7.722955 7.722955 7.722955 ZT16-19 7.094865 7.094865 7.094865 ZT20-23 6.92235 6.92235 6.92235