condition mean min max ZT0-3 8.359278 8.359278 8.359278 ZT4-7 8.0146665 8.0146665 8.0146665 ZT8-11 7.957314 7.957314 7.957314 ZT12-15 8.440218 8.440218 8.440218 ZT16-19 8.664024000000001 8.664024000000001 8.664024000000001 ZT20-23 8.1887475 8.1887475 8.1887475