condition mean min max ZT0-3 9.272915 9.272915 9.272915 ZT4-7 8.6812025 8.6812025 8.6812025 ZT8-11 10.5380405 10.5380405 10.5380405 ZT12-15 10.733832 10.733832 10.733832 ZT16-19 10.09496 10.09496 10.09496 ZT20-23 11.318582 11.318582 11.318582