condition mean min max ZT0-3 8.683023 8.683023 8.683023 ZT4-7 8.385001 8.385001 8.385001 ZT8-11 8.4379185 8.4379185 8.4379185 ZT12-15 7.7175080000000005 7.7175080000000005 7.7175080000000005 ZT16-19 8.1513145 8.1513145 8.1513145 ZT20-23 9.351752999999999 9.351752999999999 9.351752999999999