condition mean min max ZT0-3 15.139064 15.139064 15.139064 ZT4-7 16.7138405 16.7138405 16.7138405 ZT8-11 16.023474999999998 16.023474999999998 16.023474999999998 ZT12-15 20.032598 20.032598 20.032598 ZT16-19 17.785601 17.785601 17.785601 ZT20-23 19.7671165 19.7671165 19.7671165