US stocks tumbled Friday to cap a week of volatile trading as investors reacted to downbeat earnings reports from blue-chip tech firms and worrisome economic data. The Dow Jones Industrial Average plummeted 939.18 points, or 2.77%. The tech-heavy Nasdaq index fell 536.89 points, or 4.17%, and the broad-based S&P 500 sank 155.62 points, or 3.6%….

Read More