A manufacturer wants to increase the shelf life of a line of cake mixes. Past records indicate that the average shelf life of the mix is 216 days. After a revised mix has been developed, a sample of nine boxes of cake mix had a mean of 217.222 and a standard deviation of 1.2019. At the 0.025 significance level, what is the critical value? State the null and alternative hypothesis. Draw a diagram. Provide the computation of the test statistic. State your decision in terms of the null hypothesis.