condition mean min max ZT0-3 8.566686 8.566686 8.566686 ZT4-7 8.679032 8.679032 8.679032 ZT8-11 8.0439535 8.0439535 8.0439535 ZT12-15 7.8345445 7.8345445 7.8345445 ZT16-19 8.250177 8.250177 8.250177 ZT20-23 8.250177 8.250177 8.250177