condition mean min max ZT0-3 8.234197 8.234197 8.234197 ZT4-7 7.5802625 7.5802625 7.5802625 ZT8-11 7.676239 7.676239 7.676239 ZT12-15 7.0788355 7.0788355 7.0788355 ZT16-19 8.056213 8.056213 8.056213 ZT20-23 7.42858 7.42858 7.42858