condition mean min max ZT0-3 7.986423 7.986423 7.986423 ZT4-7 8.0430925 8.0430925 8.0430925 ZT8-11 7.564401 7.564401 7.564401 ZT12-15 8.263242 8.263242 8.263242 ZT16-19 8.227398 8.227398 8.227398 ZT20-23 7.485567 7.485567 7.485567