condition mean min max ZT0-3 7.847117 7.847117 7.847117 ZT4-7 8.034772 8.034772 8.034772 ZT8-11 7.924143000000001 7.924143000000001 7.924143000000001 ZT12-15 7.8410825 7.8410825 7.8410825 ZT16-19 7.667324 7.667324 7.667324 ZT20-23 8.1012875 8.1012875 8.1012875