The sustained power output of a new model of engines under production have been tested on a representative sample of 40 engines. The sample mean was x = 452kW with standard deviation s = 15.5kW. Using a 5% significance level, test whether there is evidence that the new model has power output in excess of the 450kW of the current model.Are any assumptions about the distribution of the sustained power outputs of the engines needed for this test to be valid?