condition mean min max ZT0-3 9.093636 9.093636 9.093636 ZT4-7 8.6866385 8.6866385 8.6866385 ZT8-11 7.8558495 7.8558495 7.8558495 ZT12-15 8.2354415 8.2354415 8.2354415 ZT16-19 8.356038999999999 8.356038999999999 8.356038999999999 ZT20-23 8.7289615 8.7289615 8.7289615