condition mean min max ZT0-3 2.1964992955 2.179276699 2.2137218919999997 ZT4-7 1.2473192245 1.077227059 1.41741139 ZT8-11 1.67218758925 1.4950823065 1.849292872 ZT12-15 1.643090104 1.5908854505 1.6952947575 ZT16-19 2.7402330785 2.5256224195 2.9548437375 ZT20-23 4.1257379925 3.91777618 4.333699805