9. A car maintenance rm has experienced increased demand and customers are facing an average waiting time of 4.3 weeks. It worries that they may not nd this acceptable and may go elsewhere. 50 they decide to increase the size of the maintenance garage. Six months later the owner observes that demand has increased further and doubts that the waiting time has been reduced. A random sample of 32 customers nds an average wait of 4.156 weeks. The population standard deviation is 0.574. Would you conclude that the average waiting time has been reduced? Remember to set out all the steps and assumptions in your argument