The NPD Group recently released its annual U.S. Video Game Industry Retail Sales Report. The report contained the NPD Group’s selection of the top 10 video games based on units sold. The top-selling video game was Madden NFL 2012, published by Electronic Arts. The average retail price for this video game last year was $56. The file titled Madden contains a sample of the current retail prices paid for Madden NFL 2012.
a. Calculate a 95% confidence interval for the current average retail price paid for Madden NFL 2012.
b. On the basis of the confidence interval constructed in part a, does it seem likely that the average retail price for Madden NFL 2012 has decreased? Explain.
c. What sample size would be required to generate a margin of error of $1?