condition mean min max ZT0-3 7.445435 7.445435 7.445435 ZT4-7 6.20044 6.20044 6.20044 ZT8-11 6.1376349999999995 6.1376349999999995 6.1376349999999995 ZT12-15 6.4834 6.4834 6.4834 ZT16-19 8.894110000000001 8.894110000000001 8.894110000000001 ZT20-23 6.67952 6.67952 6.67952