condition mean min max ZT0-3 14.673725 13.5567 15.79075 ZT4-7 12.87575 12.87575 12.87575 ZT8-11 15.351199999999999 15.351199999999999 15.351199999999999 ZT12-15 0 0 0 ZT16-19 18.77545 18.77545 18.77545 ZT20-23 21.4302 21.4302 21.4302