condition mean min max ZT0-3 6.759453 6.759453 6.759453 ZT4-7 7.8415680000000005 7.8415680000000005 7.8415680000000005 ZT8-11 7.531316 7.531316 7.531316 ZT12-15 8.119955000000001 8.119955000000001 8.119955000000001 ZT16-19 7.801445 7.801445 7.801445 ZT20-23 8.418865 8.418865 8.418865