condition mean min max ZT0-3 8.705496 8.705496 8.705496 ZT4-7 7.976672499999999 7.976672499999999 7.976672499999999 ZT8-11 8.4469695 8.4469695 8.4469695 ZT12-15 7.964072999999999 7.964072999999999 7.964072999999999 ZT16-19 8.9496875 8.9496875 8.9496875 ZT20-23 8.246599 8.246599 8.246599