condition mean min max ZT0-3 7.934751 7.934751 7.934751 ZT4-7 9.435571 9.435571 9.435571 ZT8-11 8.6225555 8.6225555 8.6225555 ZT12-15 9.1133675 9.1133675 9.1133675 ZT16-19 8.5053485 8.5053485 8.5053485 ZT20-23 7.75498 7.75498 7.75498