condition mean min max ZT0-3 9.29843 9.29843 9.29843 ZT4-7 8.8941965 8.8941965 8.8941965 ZT8-11 7.954299499999999 7.954299499999999 7.954299499999999 ZT12-15 8.862893 8.862893 8.862893 ZT16-19 8.243352 8.243352 8.243352 ZT20-23 7.844837 7.844837 7.844837