According to J.D. Power & Associates, the mean purchase price of a smartphone device (such as an iPhone or Blackberry) in 2008 was $216. In 2009, a random sample of 20 business managers who owned a...

According to J.D. Power & Associates, the mean purchase price of a smartphone device (such as an iPhone or Blackberry) in 2008 was $216. In 2009, a random sample of 20 business managers who owned a smartphone device showed a mean purchase price of $209 with a sample standard deviation of $13. (a) At α = .05, has the mean purchase price decreased? State the hypotheses and decision rule clearly. (b) Use Excel to find the p-value and interpret it.