Question

An automobile manufacturer claims that its car has a 57.7 miles/gallon (MPG) rating. An independent testing firm has been contracted to test the MPG for this car since it is believed that the car has an incorrect manufacturer's MPG rating. After testing 210 cars, they found a mean MPG of 57.4. Assume the standard deviation is known to be 1.9. A level of significance of 0.1 will be used. Find the value of the test statistic. Round your answer to 2 decimal places. Enter the value of the test statistic.

Answer 1

Solution :

The null and alternative hypothesis is ,

H₀ :   = 57.7

H_a :    57.7

= 57.4

= 1.9

n = 210

Test statistic = z =

= ( - ) / / n

= (57.4 - 57.7) / 1.9 / 210

Test statistic = z = -2.29