To evaluate prices, we conducted a market-basket price survey. The market basket consisted of 152 items and included national-brand non-perishables and fresh produce, meat, and dairy products. Our price comparisons table shows how each store’s prices compared to the average prices for national-brand and non-brand (fresh meat, produce, and dairy) items at three sample stores from each of the area’s two largest chains, Giant and Safeway. The survey was conducted from August 1 to 16, 2015.

The “Overall prices” tab of the price comparisons table shows how each store’s national brand non-perishables and fresh produce, meat, and dairy products stacked up. The $83 score for the Walmart Supercenter in Fairfax shows that it was about 17 percent cheaper than the Giant/Safeway average for the same products. The $101 score for Harris Teeter means that its prices were about one percent higher than the Giant/Safeway average. (Since the market basket includes fresh meat and produce, store-to-store quality differences may account for some price differences. Also, savings might vary depending on such factors as the extent to which shoppers take advantage of specials and coupons.)

For our survey, we used available sale prices and we assumed shoppers would use club cards at all stores that offered them.

The “Cheapest brands” tab of the price comparisons table shows the effect of substituting the cheapest available brand in each store for 26 national-brand items. Wegmans, with a score of $88, beat Harris Teeter’s prices by about seven percent when we substituted the cheapest brands in place of some national brands at each store.

The “Variety” tab of the price comparisons table also shows the percent of market-basket items that our shoppers found at each store. For example, the Giant in Bethesda carried 96 percent of the items in our full market basket that contains national brands.

To compare Trader Joe’s and Aldi’s prices with prices at conventional supermarkets, we used the modified survey described in the text of this article. Our section on comparing Trader Joe's and Aldi's prices describes this survey and shows the results of these comparisons.

We also used a modified survey to compare prices between conventional supermarkets and warehouse stores. Our section on warehouse stores reports those findings.

In our tab comparing stores’ Service quality, we report ratings we received from area consumers (primarily CHECKBOOK and Consumer Reports subscribers) of stores’ products and service. The survey asked respondents to rate supermarkets “inferior,” “adequate,” or “superior” on various aspects of quality, from “quality of fresh produce” to “convenience of store layout” to “overall quality.” Our ratings tables reports (for chains that received at least 10 ratings) the percentage of customers who rated it “superior” on each question.