[2] The manager of a large shipping company, from past experience, believes that the mean number of packages processed for shipping per day is 450. A new method of processing was introduced, and in a random sample of 20 days, the mean number of packages processed was found to be 460, with a standard deviation of 40. Assuming that the distribution is normal, test at the 5% level of significance, the null hypothesis Ho: u = 450 against the alternative hypothesis H1: u > 450. Is this enough evidence, to conclude that the mean number has increased? 151