condition mean min max ZT0-3 6.884655 6.884655 6.884655 ZT4-7 5.23063 5.23063 5.23063 ZT8-11 5.38613 5.38613 5.38613 ZT12-15 6.658975 6.658975 6.658975 ZT16-19 7.81634 7.81634 7.81634 ZT20-23 7.8318 7.8318 7.8318