In a 2010 automotive quality study conducted by J.D. Power & Associates, Toyota Motor Corp. was rated below average, falling to 21st place from 7th the year before (The Wall Street Journal, June 18, 2010). Toyota’s reputation suffered due to massive recalls in late 2009 and early 2010 related to defects that could cause the company’s cars to accelerate on their own. Moreover, the company was criticized for its delay in responding to the problem. Suppose that from past experience, Toyota expects complaints from 5% of new car buyers each month. For each of the last six months, the company surveys 500 new car buyers and asks if the owner has any complaints about the car. The following sample proportions are obtained:

0.065 0.075 0.082 0.086 0.090 0.092

a. Construct a chart. Plot the sample proportions on the chart.

b. Based on the results, should Toyota have any concerns? Explain. L056