condition mean min max ZT0-3 8.972078 8.972078 8.972078 ZT4-7 8.3529415 8.3529415 8.3529415 ZT8-11 9.054751499999998 9.054751499999998 9.054751499999998 ZT12-15 8.5957045 8.5957045 8.5957045 ZT16-19 8.693725 8.693725 8.693725 ZT20-23 9.135691000000001 9.135691000000001 9.135691000000001