Average of use

Question

The average age of passenger cars in use in a country is 9.0 years. For a simple random sample of 34 vehicles observed in the employee parking area of a large manufacturing plant, the average age is 10.3 years, with a standard deviation of 3.1 years. At the 0.01 level of significance, can we conclude that the average age of cars driven to work by the plant’s employees is greater than the national average?

Answer 1

We can find a t test statistic and calculate the pvalue to compare to 1%

 

t = (10.3-9)/(3.1/sqrt(34)) = 2.445237891

 

This is associated with a pvalue of .0099,

Just under 1%

 

Therefore, yes we have evidence at the 1% alpha level the average age of cars driven to work by the plants employees is greater than the national average