Refer to the Buena School District bus data.
a. Suppose we consider a bus “old” if it has been in service more than 8 years. At the .01 significance level, can we conclude that less than 40% of the district’s buses are old? Report the p-value.
b. Find the median maintenance cost and the median age of the buses. Organize the data into a two-by-two contingency table, with buses above and below the median of each variable. Determine whether the age of the bus is related to the amount of the maintenance cost. Use the .05 significance level.
c. Is there a relationship between the maintenance cost and the manufacturer of the bus? Use the breakdown in part (b) for the buses above and below the median maintenance cost and the bus manufacturers to create a contingency table. Use the .05 significance level.