condition mean min max ZT0-3 10.125647 10.125647 10.125647 ZT4-7 9.000316 9.000316 9.000316 ZT8-11 8.867315999999999 8.867315999999999 8.867315999999999 ZT12-15 7.8622285000000005 7.8622285000000005 7.8622285000000005 ZT16-19 8.4058235 8.4058235 8.4058235 ZT20-23 8.8321455 8.8321455 8.8321455