In 2011, Brand a MP3 Players Had 45% of the Market

Essay

In 2011, Brand A MP3 Players had 45% of the market, Brand B had 35%, and Brand C had 20%. This year the makers of brand C launched a heavy advertising campaign. A random sample of electronic stores shows that of 10,000 MP3 Players sold, 4,350 were Brand A, 3,450 were Brand B, and 2,200 were Brand C. Has the market changed? Test at $\alpha$ = 0.01.