Average rates on fixed mortgages ticked up this week just slightly above their record lows, keeping home-buying and refinancing attractive. Mortgage buyer Freddie Mac said Thursday that the average rate on 30-year loans ticked up to 3.34%, from last week’s 3.32%. Two weeks ago, the rate dipped to 3.31%, lowest on records dating to 1971. The average rate on 15-year fixed mortgages rose to 2.67% from 2.64% last week. The rate declined to 2.63% two weeks ago, also a record low.