condition mean min max ZT0-3 7.768585 7.768585 7.768585 ZT4-7 6.09453 6.09453 6.09453 ZT8-11 5.526885 5.526885 5.526885 ZT12-15 7.02037 7.02037 7.02037 ZT16-19 8.452345000000001 8.452345000000001 8.452345000000001 ZT20-23 8.213635 8.213635 8.213635