condition mean min max ZT0-3 7.138566 7.138566 7.138566 ZT4-7 8.907356 8.907356 8.907356 ZT8-11 7.728313 7.728313 7.728313 ZT12-15 8.1988555 8.1988555 8.1988555 ZT16-19 7.781046 7.781046 7.781046 ZT20-23 7.986423 7.986423 7.986423