condition mean min max ZT0-3 12.630575 11.8187 13.442450000000001 ZT4-7 8.449285 8.449285 8.449285 ZT8-11 4.45603 4.45603 4.45603 ZT12-15 0 0 0 ZT16-19 7.120255 7.120255 7.120255 ZT20-23 10.36712 10.36712 10.36712