condition mean min max ZT0-3 7.307705 7.307705 7.307705 ZT4-7 6.835785 6.835785 6.835785 ZT8-11 6.810795 6.810795 6.810795 ZT12-15 6.707215 6.707215 6.707215 ZT16-19 8.236225 8.236225 8.236225 ZT20-23 6.527525 6.527525 6.527525