The Wall Street Journal's Shareholder Scoreboard tracks the performance of 1000 major U.S. companies (The Wall Street Journal, March 10, 2003). The performance of each company is rated based on the annual total return, including stock price changes and the reinvestment of dividends. Ratings are assigned by dividing all 1000 companies into five groups from A (top 20%), B (next 20%), to E (bottom 20%). Shown here are the one-year ratings for a sample of 60 of the largest companies. Do the largest companies differ in performance from the performance of the 1000 companies in the Shareholder Scoreboard? Use ?= .05.
A=5, B=8, C=15, D=20, E=12