condition mean min max ZT0-3 8.025259 8.025259 8.025259 ZT4-7 8.110115 8.110115 8.110115 ZT8-11 7.698449 7.698449 7.698449 ZT12-15 8.1545285 8.1545285 8.1545285 ZT16-19 7.939493499999999 7.939493499999999 7.939493499999999 ZT20-23 8.268430500000001 8.268430500000001 8.268430500000001