The average weight of a package of rolled oats is supposed to be at least 18 ounces. A sample of 18 packages shows a mean of 17.78 ounces with a standard deviation of 0.41 ounce.
(a) At the 5 percent level of significance, is the true mean smaller than the specification? Clearly state your hypotheses and decision rule.
(b) Is this conclusion sensitive to the choice of?
(c) Use Excel to find the p-value. Interpret it.