The Federal Reserve Bank of Chicago said today that its index of Midwest manufacturing activity increased 0.8 percent in February, to a seasonally adjusted level of 96.3. Revised data show the index was up 0.4 percent in January. The Federal Reserve Board's industrial production index for manufacturing moved up 0.6 percent in February. Regional output rose 5.9 percent in February from a year earlier, and national output increased 2.4 percent.