condition mean min max ZT0-3 8.250177 8.250177 8.250177 ZT4-7 8.158116 8.158116 8.158116 ZT8-11 9.399447 9.399447 9.399447 ZT12-15 8.656942 8.656942 8.656942 ZT16-19 8.312289 8.312289 8.312289 ZT20-23 8.3080605 8.3080605 8.3080605