Image: Sony.

January was a terrible month for the stock market, but Friday at least put a dent in the losses that the major market benchmarks suffered during the month. The Dow and S&P 500 both soared around 2.5% after the Bank of Japan renewed the long tradition among global central banks in making efforts to stimulate the Japanese economy and fight against deflation.

Even though the negative interest rate policy that the BoJ adopted wasn't terribly successful in Europe when the European Central Bank used it, investors remain hopeful that the move will restore confidence in the future prospects for macroeconomic growth. Many stocks pushed forward strongly on Friday, and among the best were Sony (NYSE:SNE), Micron Technology (NASDAQ:MU), and Select Comfort (NASDAQ:SNBR).

Sony soared 18% on a combination of positive news. First, the BoJ's move definitely contributed to the optimism for the electronics manufacturer, because so much of its business comes from exports that benefit from the weakness in the Japanese yen that the central bank's move brought about Friday. More importantly, though, Sony reported strong financial results for its holiday quarter, citing increased sales of its PlayStation 4 game console, as well as strong box-office performance from a couple of its movie releases. Even though Sony didn't produce growth in the smartphone or device segments, investors were willing to overlook that in favor of what it hopes will be even better growth opportunities in the businesses that gives Sony its best chance for long-term growth.

Micron Technology jumped 12% after investors finally chose to recognize that the memory-chip maker might represent a valid bargain opportunity. The stock has fallen dramatically during the past year because of a renewed price war among major players in the memory market. Despite what appeared to be extremely cheap valuations, projections for Micron earnings have fallen along with the stock.

The question that Micron has to answer is whether the oversupply-related slump in the memory-chip industry will produce as deep a decline as it has in previous cycles. From today's movement in the stock, Micron investors appear to be ready to bet that the answer is no, and that a generally strong technology sector could start pushing chip demand higher. If that happens, then Micron has plenty of upside left.

Finally, Select Comfort rose 12%. The mattress maker got an upgrade from analysts at Wedbush, who said that they noticed better trends in the company's sales in recent weeks.

Select Comfort has also pushed forward with marketing campaigns that tout its high satisfaction rates among customers, and investors expect that those efforts should help the stock regain some of its recent losses. Even with today's jump, the mattress company still has lost more than a third of its value over the past year or so. Given how well the housing market has performed over that span, investors would prefer to see better results from Select Comfort going forward.