condition mean min max ZT0-3 6.269914 6.269914 6.269914 ZT4-7 7.0733645 7.0733645 7.0733645 ZT8-11 7.8955105 7.8955105 7.8955105 ZT12-15 7.367586 7.367586 7.367586 ZT16-19 7.348677 7.348677 7.348677 ZT20-23 6.953670499999999 6.953670499999999 6.953670499999999