A critic of Canada Post claims that its financial returns are typically $200 million less than forecast. In five of the years of the 1990s, the mean difference (in millions of dollars) between Canada Post's forecast and actual financial positions was 218.8, with a standard deviation of 118.76 (based on Canada Post data reported by Maclean Hunter, 1996). Use a significance level of 0.05 to test the claim that the mean difference between forecasted returns and actual returns was 200.
Use the traditional approach summarized. Draw a graph showing the test statistic and critical values. In each case, assume that the population has a distribution that is approximately normal and that the sample is randomly selected.