condition mean min max ZT0-3 8.130646 8.130646 8.130646 ZT4-7 7.2664075 7.2664075 7.2664075 ZT8-11 7.8879055000000005 7.8879055000000005 7.8879055000000005 ZT12-15 8.135847 8.135847 8.135847 ZT16-19 8.472398 8.472398 8.472398 ZT20-23 7.71428 7.71428 7.71428