The management of a company claim that the average weekly earnings (including overtime payments) of their employees is £850. The local trade union official disputes this figure, believing that the average earnings are lower. In order to test this claim, a random sample of 150 employees was selected from the payroll. The sample average was calculated to be £828 and the sample standard deviation to be £183.13. Use an appropriate test at the 5 per cent level to determine which side of the argument you agree with.