condition mean min max ZT0-3 8.948263 8.948263 8.948263 ZT4-7 8.485121 8.485121 8.485121 ZT8-11 8.5650525 8.5650525 8.5650525 ZT12-15 8.5358215 8.5358215 8.5358215 ZT16-19 8.060027999999999 8.060027999999999 8.060027999999999 ZT20-23 8.774902 8.774902 8.774902