condition mean min max ZT0-3 8.298502 8.298502 8.298502 ZT4-7 8.214573999999999 8.214573999999999 8.214573999999999 ZT8-11 8.5055955 8.5055955 8.5055955 ZT12-15 8.338022500000001 8.338022500000001 8.338022500000001 ZT16-19 8.2005215 8.2005215 8.2005215 ZT20-23 8.643449 8.643449 8.643449