condition mean min max ZT0-3 8.130646 8.130646 8.130646 ZT4-7 7.9735605000000005 7.9735605000000005 7.9735605000000005 ZT8-11 7.8827775 7.8827775 7.8827775 ZT12-15 8.319334999999999 8.319334999999999 8.319334999999999 ZT16-19 7.9494584999999995 7.9494584999999995 7.9494584999999995 ZT20-23 7.8846335 7.8846335 7.8846335