Last Year, Brand a Mobile Android Phones Had 45% of the Market

Essay

Last year, Brand A mobile android phones 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 mobile phone stores shows that of the 10 000 android mobile phones sold, 4350 were Brand A, 3450 were Brand B, and 2200 were Brand
C. Has the market changed? Test at $\alpha =$ 0.05.