condition mean min max ZT0-3 8.426391 8.426391 8.426391 ZT4-7 8.7444085 8.7444085 8.7444085 ZT8-11 7.9466535 7.9466535 7.9466535 ZT12-15 8.0039985 8.0039985 8.0039985 ZT16-19 7.9568605 7.9568605 7.9568605 ZT20-23 8.766295 8.766295 8.766295