Following days of sharp volatility, stocks drifted lower today in a quiet day on Wall Street. Preliminary calculations show the Dow Jones industrial average fell 15.17 to 5,568.72. Volume was moderate at under 400 million shares traded. Broad market indexes were higher, with the Nasdaq composite lifted by technology stocks. The Nasdaq composite index rose 14.25 to 1,087.30. Stocks were helped a little by bonds, where the long bond was up 3-16 pointS, yielding 6.67 percent, recovering from a 1/2-point loss this morning. At the American Stock Exchange, the market value index rose 1.60 to 560.77.