condition mean min max ZT0-3 9.707831 9.707831 9.707831 ZT4-7 9.0214575 9.0214575 9.0214575 ZT8-11 8.6062325 8.6062325 8.6062325 ZT12-15 8.315257 8.315257 8.315257 ZT16-19 8.4780195 8.4780195 8.4780195 ZT20-23 8.733635 8.733635 8.733635