condition mean min max ZT0-3 6.669514 6.669514 6.669514 ZT4-7 7.4208735 7.4208735 7.4208735 ZT8-11 7.2702295 7.2702295 7.2702295 ZT12-15 6.932428 6.932428 6.932428 ZT16-19 7.457266499999999 7.457266499999999 7.457266499999999 ZT20-23 7.5766265 7.5766265 7.5766265