Fixed mortgage rates dipped to new all-time record lows last week, helping to boost sales of new and used homes, according to Freddie Mac’s weekly nationwide survey.

The 30-year fixed-rate mortgage averaged 3.34 percent, down from 3.40 percent a week earlier. One year ago, the 30-year rate averaged 4.00 percent.

Fifteen-year mortgages averaged 2.65 percent, down from 2.69 percent.

Five-year hybrid adjustable-rate mortgages (ARMs) edged up a little, averaging 2.74 percent compared to 2.73 percent the week before.

One-year ARMs averaged 2.55 percent, down from 2.59 percent.