A local Indian restaurant advertises home delivery times of 30 minutes. To monitor the effectiveness of this promise the restaurant manager monitors the time that the order was received and the time...

A local Indian restaurant advertises home delivery times of 30 minutes. To monitor the effectiveness of this promise the restaurant manager monitors the time that the order was received and the time of delivery. Based upon historical data the average time for delivery is 30 minutes with a standard deviation of 5 minutes. After a series of complaints from customers regarding this promise the manager decided to analyse the data of the last 50 orders which resulted in an average time of 32 minutes. Conduct an appropriate test at a significance level of 5%. Should the manager be concerned?