An automobile manufacturer claims that their jeep has a 28.6 miles/gallon (MPG) rating. An independent testing firm has been contracted to test the MPG for this jeep. After testing 240 jeeps they found a mean MPG of 29.0. Assume the variance is known to be 6.25. Is there sufficient evidence at the 0.05 level that the jeeps have an incorrect manufacturer's MPG rating?
