condition mean min max ZT0-3 12.086561 12.086561 12.086561 ZT4-7 9.350162999999998 9.350162999999998 9.350162999999998 ZT8-11 9.0976925 9.0976925 9.0976925 ZT12-15 8.930569 8.930569 8.930569 ZT16-19 9.851901999999999 9.851901999999999 9.851901999999999 ZT20-23 8.7435745 8.7435745 8.7435745