condition mean min max ZT0-3 2.1269983333333333 2.02159 2.232135 ZT4-7 2.436045 2.436045 2.436045 ZT8-11 2.5185500000000003 2.5185500000000003 2.5185500000000003 ZT12-15 3.692875 3.69225 3.6935 ZT16-19 2.363085 2.363085 2.363085 ZT20-23 2.001355 2.001355 2.001355