Some retailers reported stronger-than-expected November sales on Thursday, helped by a post-Thanksgiving rush and holiday discounts, but notable misses by others and a shift in the retail calendar left an unclear picture of the strength of the key holiday season.

Results from discounters Target Corp (TGT.N: Quote, Profile, Research) and Family Dollar Stores Inc (FDO.N: Quote, Profile, Research) fell short of analysts' expectations, as more consumers -- and no longer just those with low incomes -- tightened their wallets in the face of rising food and fuel costs, increasing mortgage rates and tighter credit.

November's numbers provide a good snapshot of the state of the shopper this holiday. Upper-income shoppers are driving good results among some retailers, while lower- and increasingly middle-income shoppers drag down results at other retailers, said Frank Badillo, senior economist for consulting firm TNS Retail Forward.

Patricia Walker, a senior executive with consulting firm Accenture's retail practice, said the results were a mixed bag. Retailers that took advantage of all the publicity around Black Friday, the day after the U.S. Thanksgiving holiday that traditionally kicks off the holiday shopping season, were able to boost sales, she added.

The key question for all of these retailers is: Can they keep the momentum going in December? Walker said.

The Standard & Poor's Retail Index .RLX was down 0.8 percent in early afternoon trade, compared with 0.6 percent increases for both the S&P 500 Index .SPX and Dow Jones Industrial Average .DJI, respectively.

A shift in the monthly retail reporting calendar boosted some November same-store sales figures, but will deflate some results in December, helping to disguise the month's true winners and losers.

Target, whose shares were down more than 7 percent, said sales at stores open at least a year, adjusted for the calendar shift, rose 1.1 percent in November, below its expected range of 2 to 4 percent.

If the recent soft trends continued, Target said, its December sales could also miss its forecast.

Target's warning is cause for concern when coupled with comments from other retailers that sales last week were sluggish even after the Black Friday hype, said Ken Perkins, president of research firm Retail Metrics.

Discount rival Wal-Mart Stores Inc (WMT.N: Quote, Profile, Research) said U.S. same-store sales rose 1.5 percent in November, and results were solid as the holiday rush got under way.

The world's largest retailer made an early push to try to drive holiday sales, cutting prices on more than 15,000 items.

Wal-Mart's same-store sales increase was slightly better than analysts had expected and within its planned range. But sales at its namesake stores continue to lag, and it forecast a U.S. same-store sales gain of 1 to 3 percent for the holiday-heavy month of December.

Investors will try to sort through the numbers and the impact of the calendar shift to glean insight into the strength of consumer spending, which makes up two-thirds of the U.S. economy.

Apparel retailers, on average, posted a 1.5 percent increase in November same-store sales, according to a sales-weighted index tracked by Standard & Poor's analyst Marie Driscoll. She said it beat her 1 percent projection and the year-earlier increase of 1.1 percent.

An early Thanksgiving benefited retailers as shoppers flocked to stores on Black Friday, and weekend mall traffic rose 4.8 percent, Driscoll wrote in a research note. But most retailers experienced a slowdown in the final November week, and we would not extrapolate strength forward.

AnnTaylor Stores Corp (ANN.N: Quote, Profile, Research), whose shares were down 4.5 percent in midday trade, said its namesake chain experienced very soft traffic in the second half of the month, and traffic deteriorated as time went on.

Department stores, many of which benefited from the calendar shift, offered an unclear picture. Sales at Kohl's Corp (KSS.N: Quote, Profile, Research), Macy's Inc (M.N: Quote, Profile, Research), Nordstrom Inc (JWN.N: Quote, Profile, Research) and Saks Inc (SKS.N: Quote, Profile, Research) topped expectations, while those at J.C. Penney Co Inc (JCP.N: Quote, Profile, Research), Dillard's Inc (DDS.N: Quote, Profile, Research) and Bon-Ton Stores Inc (BONT.O: Quote, Profile, Research) missed.

We anticipate a challenging retail month ahead, uncomfortable for most retailers as much of the business will come at the end of the month, wrote Stifel Nicolaus analyst Richard Jaffe in a research note. Judicious use of discounts and promotions will likely be key to driving sales while preserving margins as consumers procrastinate.