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

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 $\alpha$ = .01.