Refer to Example 9.7. The quality control manager wants to know whether the daily yield at a local chemical plant-which has averaged 880 metric tons for the last several years has changed in recent months. A random sample of 50 days gives an average yield of 871 metric tons with a standard deviation of 21 metric tons. Calculate the p-value for this two-tailed test of hypothesis. Use the p-value to draw conclusions re- garding the statistical test.