Trader Joe's is the top grocery store chain in North America, according to one study. Customers weren't surprised.

Market Force, a customer intelligence firm, polled 6,600 consumers on supermarket satisfaction. Trader Joe's, famous for low prices, happy checkers, and Two Buck Chuck (actually more than $2 these days), ranked as the store most likely to be recommended to friends and family.

"I just love the prices they really keep them nice and low," said shopper Anna Edsall. "People are always super friendly and helpful and knowledgeable and they have very unique products that you can't really find other places."

Customers considered convenient locations, low prices and good sales and promotions as factors.

Trader Joe's was chosen as the overall favorite, while Ralph's was picked as having the most convenient locations. Walmart was voted least likely to be recommended by guests and had the lowest satisfaction score.

The survey was conducted in May 2013 across the United States and Canada.