Nasdaq closes lower to end worst week since March

NEW YORK -- Wall Street closed out its worst week since June with another day of churning trading Friday, as big technology stocks resumed their suddenly weakened ways. The S&P 500 rose 1.78, or 0.05%, to 3,340.97, but only after a roller-coaster day where a gain of 0.9% gave way to a loss of 0.9%. It kept swinging up and down after that, the latest examples of the lightning-quick shifts in momentum that have rocked Wall Street recently. Through the tumultuous week, the S&P 500 lost 2.5% to clinch its its first back-to-back weekly loss in four months. The...