A sample of 64 observations has been selected to test whether the population mean is smaller than 15. The sample showed an average of 14.5 and a standard deviation of 4.7. You want to test this hypothesis at 95% level of confidence using the critical value approach. First, compute the critical value and the test statistics associated with this test. Second, compute the difference between the test statistic and the critical value (test statistic - critical value). What is this difference