An srs of 100 postal employees found that the average time these employees had worked for the postal service was = 7 years, with standard deviation s = 2 years. assume the distribution of the time the population of employees has worked for the postal service is approximately normal, with mean μ. are these data evidence that μ has changed from the value of 7.5 years of 20 years ago? to determine this, we test the hypotheses h0: μ = 7.5, ha: μ ≠ 7.5