condition mean min max ZT0-3 8.491532 8.491532 8.491532 ZT4-7 8.3093345 8.3093345 8.3093345 ZT8-11 8.8135875 8.8135875 8.8135875 ZT12-15 8.2655125 8.2655125 8.2655125 ZT16-19 8.6022975 8.6022975 8.6022975 ZT20-23 8.761070499999999 8.761070499999999 8.761070499999999