condition mean min max ZT0-3 15.244616 15.244616 15.244616 ZT4-7 18.9605075 18.9605075 18.9605075 ZT8-11 23.8535045 23.8535045 23.8535045 ZT12-15 21.271656 21.271656 21.271656 ZT16-19 24.6804645 24.6804645 24.6804645 ZT20-23 22.284703999999998 22.284703999999998 22.284703999999998