condition mean min max ZT0-3 16.856603 16.856603 16.856603 ZT4-7 17.991832 17.991832 17.991832 ZT8-11 18.1322295 18.1322295 18.1322295 ZT12-15 15.9666665 15.9666665 15.9666665 ZT16-19 17.025737999999997 17.025737999999997 17.025737999999997 ZT20-23 16.019787 16.019787 16.019787