Chapter 6, Problem 68CP

Used car deals Refer to the previous exercise. Suppose carmax.com decides to highlight any used car that is priced 1.5 standard deviations below the mean price as a special deal on its Web site.

1. a. If the distribution of used-car prices is normal, what percentage of used Audi A4s will be highlighted?
2. b. If the distribution of used-car prices is normal, what percentage of used Honda Civics will be highlighted? (Do you need to know the mean and standard deviation for used Honda Civics?)
3. c. If the distribution of used-car prices is in fact skewed to the right, will the percentage of used Audi A4s that are highlighted most likely be smaller or larger than the one from part a? Explain.

6.67 Used car prices Data from the Web site carmax.com compiled in July 2014 show that prices for used Audi A4 cars advertised on the Web site have a mean of $23,800 and a standard deviation of $4,380. Assume a normal distribution for the price.

1. a. What percent of used Audi A4s cost more than $25,000?
2. b. What percent of used Audi A4s cost between $18,000 and $22,000?
3. c. The least expensive 10% of used Audi A4s offered on the Web site cost at most how much?