Google became a publicly traded company in August 2004. Initially, the stock traded over 10 million shares each day! Since the initial offering, the volume of stock traded daily has decreased substantially. In 2007, the mean daily volume in Google stock was 5.44 million shares, according to Yahoo!Finance. A random sample of 35 trading days in 2010 resulted in a sample mean of 3.28 million shares with a standard deviation of 1.68 million shares.

(a) Based on the histogram and boxplot shown (from StatCrunch), why is a large sample necessary to conduct a hypothesis test about the mean?

(b) Does the evidence suggest that the volume of Google stock has changed since 2007? Use the a = 0.05 level of significance.

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