condition mean min max ZT0-3 8.435038 8.435038 8.435038 ZT4-7 8.9142315 8.9142315 8.9142315 ZT8-11 8.584188000000001 8.584188000000001 8.584188000000001 ZT12-15 8.137065 8.137065 8.137065 ZT16-19 9.135175 9.135175 9.135175 ZT20-23 8.2298635 8.2298635 8.2298635