condition mean min max ZT0-3 8.297405 8.297405 8.297405 ZT4-7 9.3386525 9.3386525 9.3386525 ZT8-11 8.2074985 8.2074985 8.2074985 ZT12-15 8.130792 8.130792 8.130792 ZT16-19 9.027027499999999 9.027027499999999 9.027027499999999 ZT20-23 7.4568625 7.4568625 7.4568625